Ebooks, Fiction, Non-Fiction 1000s of Free books and stories online to read now ~ Main Page

 

 

 

The Invisible Death by Victor Rousseau

A COMPLETE NOVELETTE

 

CHAPTER I

Out of the Hangman's Hands

Y

ou speak," said Von Kettler, jeering, "as if you really believed that you had the power of life and death over me."

With night-rays and darkness-antidote America strikes back at the terrific and destructive Invisible Empire.

The Superintendent of the penitentiary frowned, yet there was something of perplexity in the look he gave the prisoner. "Von Kettler, I think it is time that you dropped this absurd pose of yours," he said, "in view of the fact that you are scheduled to die by hanging at eight o'clock to-morrow night. Your life and death are in your own hands."

Von Kettler bowed ironically. Standing in the Superintendent's presence in the uniform of the condemned cell, collarless, bare-headed, he yet seemed to dominate the other by a certain poise, breeding, nonchalance.

"Your life is offered you in consideration of your making a complete written confession of the whole ramifications of the plot against the Federal Government," the Superintendent continued.

"Rather a confession of weakness, my dear Superintendent," jeered the prisoner.


O

h don't worry about that! The Government has unravelled a good deal of the conspiracy. It knows that you and your international associates are planning to strike at civilized government throughout the world, in the effort to restore the days of autocracy. It knows you are planning a world federation of states, based on the principles of absolutism and aristocracy. It is aware of the immense financial resources behind the movement. Also that you have obtained the use of certain scientific discoveries which you believe will aid you in your schemes."

"I was wondering," jeered the prisoner, "how soon you were coming to that."

"They didn't help you in your murderous scheme," the Superintendent thundered. "You were found in the War Office by the night watchman, rifling a safe of valuable documents. You shot him with a pistol equipped with a silencer. You shot down two more who, hearing his cries, rushed to his aid. And you attempted to stroll out of the building, apparently under the belief that you possessed mysterious power which would afford you security."

"A little lapse of judgment such as may happen with the best laid plans," smiled Von Kettler. "No, Superintendent, I'll be franker with you than that. My capture was designed. It was decided to give the Government an object lesson in our power. It was resolved that I should permit myself to be captured, in order to demonstrate that you cannot hang me, that I have merely to open the door of my cell, the gates of this penitentiary, and walk out to freedom."

"Have you quite finished?" rasped the Superintendent.

"At your disposal," smiled the other.

"Here's your last chance, Von Kettler. Your persistence in this absurd claim has actually shaken the expressed conviction of some of the medical examiners that you are sane. If you will make that complete written confession that the Government asks of you, I pledge you that you shall be declared insane to-night, and sent to a sanitarium from which you will be permitted to escape as soon as this affair has blown over."


T

he United States Government has sunk pretty low, to involve itself in a deal of this character, don't you think, my dear Superintendent?" jeered Von Kettler.

"The Government is prepared to act as it thinks best in the interests of humanity. It knows that the death of one wretched murderer such as yourself is not worth the lives of thousands of innocent men!"

"And there," smiled Von Kettler, without abating an atom of his nonchalance, "there, my dear Superintendent, you hit the nail on the head. Only, instead of thousands, you might have said millions."

Von Kettler's aspect changed. Suddenly his eyes blazed, his voice shook with excitement, his face was the face of a fanatic, of a prophet.

"Yes, millions, Superintendent," he thundered. "It it a holy cause that inspires us. We know that it is our sacred mission to save the world from the drabness of modern democracy. The people—always the people! Bah! what are the lives of these swarming millions worth when compared with a Caesar, a Napoleon, an Alexander, a Charlemagne? Nothing can stop us or defeat us. And you, with your confession of defeat, your petty bargaining—I laugh at you!"

"You'll laugh on the gallows to-morrow night!" the Superintendent shouted.

Again Von Kettler was the calm, superior, arrogant prisoner of before. "I shall never stand on the gallows trap, my dear Superintendent, as I have told you many times," he replied. "And, since we have reached what diplomacy calls a deadlock, permit me to return to my cell."

The Superintendent pressed a button on his desk; the guards, who had been waiting outside the office, entered hastily. "Take this man back," he commanded, and Von Kettler, head held high, and smiling, left the room between them.


T

he Superintendent pressed another button, and his assistant entered, a rugged, red-haired man of forty—Anstruther, familiarly known as "Bull" Anstruther, the man who had in three weeks reduced the penitentiary from a place of undisciplined chaos to a model of law and order. Anstruther knew nothing of the Superintendent's offer to Von Kettler, but he knew that the latter had powerful friends outside.

"Anstruther, I'm worried about Von Kettler," said the Superintendent. "He actually laughed at me when I spoke of the possibility of another medical examination. He seemed confident that he could not be hanged. Swore that he will never stand on the gallows trap. How about your precautions for to-morrow night?"

"We've taken all possible precautions," answered Anstruther. "Special armed guards have been posted at every entrance to the building. Detectives are patrolling all streets leading up to it. Every car that passes is being scrutinized, its plate numbers taken, and forwarded to the Motor Bureau. There's no chance of even an attempt at rescue—literally none."

"He's insane," said the Superintendent, with conviction, and the words filled him with new confidence. It had been less Von Kettler's statements than the man's cool confidence and arrogant superiority that had made him doubt. "But he's not too insane to have known what he was doing. He'll hang."

"He certainly will," replied Anstruther. "He's just a big bluff, sir."

"Have him searched rigorously again to-morrow morning, and his cell too—every inch of it, Anstruther. And don't relax an iota of your precautions. I'll be glad when it's all over."

He proceeded to hold a long-distance conversation with Washington over a special wire.


I

n his cell, Von Kettler could be seen reading a book. It was Nietzsche's "Thus Spake Zarathusta," that compendium of aristocratic insolence that once took the world by storm, until the author's mentality was revealed by his commitment to a mad-house. Von Kettler read till midnight, closely observed by the guard at the trap, then laid the word aside with a yawn, lay down on his cot, and appeared to fall instantly asleep.

Dawn broke. Von Kettler rose, breakfasted, smoked the perfecto that came with his ham and eggs, resumed his book. At ten o'clock Bull Anstruther came with a guard and stripped him to the skin, examining every inch of his prison garments. The bedding followed; the cell was gone over microscopically. Von Kettler, permitted to dress again, smiled ironically. That smile stirred Anstruther's gall.

"We know you're just a big bluff, Von Kettler," snarled the big man. "Don't think you've got us going. We're just taking the usual precautions, that's all."

"So unnecessary," smiled Von Kettler. "To-night I shall dine at the Ambassador grill. Watch for me there. I'll leave a memento."

Anstruther went out, choking. Early in the afternoon two guards came for Von Kettler.

"Your sister's come to say good-by to you," he was told, as he was taken to the visitors' cell.

This was a large and fairly comfortable cell in a corridor leading off the death house, designed to impress visitors with the belief that it was the condemned man's permanent abode; and, by a sort of convention, it was understood that prisoners were not to disabuse their visitors' minds of the idea. The convention had been honorably kept. The visitor's approach was checked by a grill, with a two-yards space between it and the bars of the cell. Within this space a guard was seated: it was his duty to see that nothing passed.


A

s soon as Von Kettler had been temporarily established in his new quarters, a pretty, fair-haired young woman came along the corridor, conducted by the Superintendent himself. She walked with dignity, her bearing was proud, she smiled at her brother through the grill, and there was no trace of weeping about her eyes.

She bowed with pretty formality, and Von Kettler saluted her with an airy wave of the hand. Then they began to speak, and the German guard who had been selected for the purpose of interpreting to the Superintendent afterward, was baffled.

It was not German—neither was it French, Italian, or any of the Romance languages. As a matter of fact, it was Hungarian.

Not until the half-hour was up did they lapse into English, and all the while they might have been conversing on art, literature, or sport. There was no hint of tragedy in this last meeting.

"Good-by, Rudy," smiled his sister, "I'll see you soon."

"To-night or to-morrow," replied Von Kettler indifferently.

The girl blew him a kiss. She seemed to detach it from her mouth and extend it through the grill with a graceful gesture of the hand, and Von Kettler caught it with a romantic wave of the fingers and strained it to his heart. But it was only one of those queer foreign ways. Nothing was passed. The alert guard, sitting under the electric light, was sure of that.

They searched Von Kettler again after he was back in the death house. The other cells were empty. In three of them detectives were placed. In the yard beyond the hangman was experimenting with the trap. He himself was under close observation. Nothing was being left to chance.


A

t seven o'clock two men collided in the death-house entrance. One was a guard, carrying Von Kettler's last meal on a tray. He had demanded Perigord truffles and paté de foie gras, cold lobster, endive salad, and near-beer, and he had got them. The other was the chaplain, in a state of visible agitation.

"If he was an atheist and mocked at me it wouldn't be so bad," the good man declared. "I've had plenty of that kind. But he says he's not going to be hanged. He's mad, mad as a March hare. The Government has no right to send an insane man to the gallows."

"All bluff, my dear Mr. Wright," answered the Superintendent, when the chaplain voiced his protest. "He thinks he can get away with it. The commission has pronounced him sane, and he must pay the penalty of his crime."

By that mysterious process of telegraphy that exists in all penal institutions, Von Kettler's boast that he would beat the hangman had become the common information of the inmates. Bets were being laid, and the odds against Von Kettler ranged from ten to fifteen to one. It was generally agreed, however, that Von Kettler would die game to the last.

"You all ready, Mr. Squires?" the prowling Superintendent asked the hangman.

"Everything's O. K., sir."

The Superintendent glanced at the group of newspaper men gathered about the gallows. They, too, had heard of the prisoner's boast. One of them asked him a question. He silenced him with an angry look.

"The prisoner is in his cell, and will be led out in ten minutes. You shall see for yourselves how much truth there it in this absurdity," he said.


H

e looked at his watch. It lacked five minutes of eight. The preparations for an execution had been reduced almost to a formula. One minute in the cell, twenty seconds to the trap, forty seconds for the hangman to complete his arrangements: two minutes, and then the thud of the false floor.

Four minutes of eight. The little group had fallen silent. The hangman furtively took a drink from his hip-pocket flask. Three minutes! The Superintendent walked back to the door of the death house and nodded to the guard.

"Bring him out quick!" he said.

The guard shot the bolt of Von Kettler's cell. The Superintendent saw him enter, heard a loud exclamation, and hurried to his side. One glance told him that the prisoner had made good his boast.

Von Kettler's cell was empty!

CHAPTER II

Conference

C

aptain Richard Rennell, of the U. S. Air Service, but temporarily detached to Intelligence, thought that Fredegonde Valmy had never looked so lovely as when he helped her out of the cockpit.

Her dark hair fell in disorder over her flushed cheeks, and her eyes were sparkling with pleasure.

"A thousand thanks, M'sieur Rennell," she said, in her low voice with its slight foreign intonation. "Never have I enjoyed a ride more than to-day. And I shall see you at Mrs. Wansleigh's ball to-night?"

"I hope so—if I'm not wanted at Headquarters," answered Dick, looking at the girl in undisguised admiration.

"Ah, that Headquarters of yours! It claims so much of your time!" she pouted. "But these are times when the Intelligence Service demands much of its men, is it not so?"

"Who told you I was attached to Intelligence?" demanded Dick bluntly.

She laughed mockingly. "Do you think that is not known all over Washington?" she asked. "It is strange that Intelligence should act like the—the ostrich, who buries his head in the sand and thinks that no one sees him because it is hidden."

Dick looked at the girl in perplexity. During the past month he had completely lost his head and heart over her, and he was trying to view her with the dispassionate judgment that his position demanded.

As the niece of the Slovakian Ambassador, Mademoiselle Valmy had the entry to Washington society. The Ambassador was away on leave, and she had appeared during his absence, but she had been accepted unquestionably at the Embassy, where she had taken up her quarters, explaining—as the Ambassador confirmed by cable—that she had sailed under a misconception as to the date of his leave.


B

runette, beautiful, charming, she had a score of hearts to play with, and yet Dick flattered himself that he stood first. Perhaps the others did too.

"Of course," the girl went on, "with the Invisible Emperor threatening organized society, you gentlemen find yourselves extremely busy. Well, let us hope that you locate him and bring him to book."

"Sometimes," said Dick slowly, "I almost think that you know something about the Invisible Emperor."

Again she laughed merrily. "Now, if you had said that my sympathies were with the Invisible Emperor, I might have been surprised into an acknowledgment," she answered. "After all, he does stand for that aristocracy that has disappeared from the modern world, does he not? For refinement of manners, for beauty of life, for all those things men used to prize."

"Likewise for the existence of the vast body of the nation in ignorance and poverty, in filth and squalor," answered Dick. "No, my sympathies are with law and order and democracy, and your Invisible Emperor and his crowd are simply a gang of thieves and hold-up men."

"Be careful!" A warning fire burned in the girl's eyes. "At least, it is known that the Emperor's ears are long."

"So are a jackass's," retorted Dick.

He was sorry next moment, for the girl received his answer in icy silence. In his car, which conveyed them from the tarmac to the Embassy, she received all his overtures in the same silence. A frigid little bow was her farewell to him, while Dick, struggling between resentment and humiliation, sat dumb and wretched at the wheel.

Yet the idea that Fredegonde Valmy had any knowledge of the conspiracy or its leaders never entered Dick's head. He was only miserable that he had offended her, and he would have done anything to have straightened out the trouble.


I

t seemed impossible that in the year 1940 the peace of the civilized world could be threatened by an international conspiracy bent on restoring absolutism, and yet each day showed more clearly the immense ramifications of the plot. Each day, too, brought home to the investigating governments more clearly the fact that the things they had discovered were few in number in comparison with those they had not.

The headquarters of the conspirators had never been discovered, and it was suspected that the powerful mind behind them was intentionally leading the investigators along false trails.

The conspiracy was world-wide. It had been behind the revolution that had recreated an absolutist monarchy in Spain. It had plunged Italy into civil war. It had thrown England into the convulsions of a succession of general strikes, using the communist movement as a cloak for its activities.

But nobody dreamed that America could become a fertile field for its insidious propaganda. Yet it was behind the millions of adherents of the so-called Freemen's Party, clamoring for the destruction of the constitution. Upon the anarchy that would follow the absolutist regime was to be erected.

Already the mysterious powers had struck. Departments of State had been entered and important papers abstracted. The Germania had mysteriously disappeared in mid-Atlantic, and a shipping panic had ensued. There were tales of mysterious figures materializing out of nothingness. It was known that the conspirators were in possession of certain chemical and electrical devices with which they hoped to achieve their ends.

The Superintendent of the penitentiary had had in his pocket an authorization to stop the execution of Von Kettler after he stood on the trap. Dead, he would be a mere mark of vengeance: alive, he might be persuaded to furnish some clue to the headquarters of the miscreants.


A

nd behind the conspirators loomed the unknown figure that signed itself the Invisible Emperor—in the communications that poured in to the White House and to the rulers of other nations. In the threats that were materializing with stunning swiftness.

Who was he? Rumor said that a former European ruler had not died as was supposed: that a coffin weighted with lead had been buried, and that he himself in his old age, had gone forth to a mad scheme of world conquest with a body of his nobles.

It had been practically a state of war since the shipment of gold, guarded by a detachment of police, had been stolen in broad daylight outside Baltimore, the police clubbed and killed by invisible assailants—as they claimed. The press was under censorship, troops under arms, and it was reported that the fleet was mobilizing.

In the midst of it all, Washington shopped, danced, feasted, flirted, like a swarm of may flies over a treacherous stream.

Intelligence was alert. As Dick started to drive away from the Slovakian Embassy, a man stepped quickly to the side of the car and thrust an envelope into his hand. Dick opened it quickly. He was wanted by Colonel Stopford at once, not at the camouflaged Headquarters at the War Department, but at the real Headquarters where no papers were kept but weighty decisions were made. And to that devious course the Government had already been driven.

Dick parked his car in a side street—it would have been under espionage in any of the official parking places—and set off at a smart walk toward his destination. Nobody would have guessed, from the appearance of the streets, that a national calamity was impending. The shopping crowds were swarming along the sidewalks, cars tailed each other through the streets; only a detachment of soldiers on the White House lawn lent a touch of the martial to the scene.


T

he building which Dick entered was an ordinary ten-story one in the business section; the various legal firms and commercial concerns that occupied it would have been greatly surprised to have known the identity of the Ira T. Graves, Importer, whose name appeared in modest letters upon the opaque glass door on the seventh story. Inside a flapper stenographer—actually one of the most trusted members of Intelligence's staff—asked Dick's name, which she knew perfectly well. Not a smile or a flicker of an eyelid betrayed the fact.

"Mr. Rennell," said Dick with equal gravity.

The girl passed into an inner room, and a buzzer sounded. In a few moments the girl came back.

"Mr. Graves will be here in a few minutes, Mr. Rennell, if you'll kindly wait in his office," she said.

Dick thanked her, and walked through into the empty office. He waited there till the girl had closed the door behind him, then went out by another door and found himself again in the corridor. Opposite him was a door with the words "Entrance 769" and a hand pointing down the corridor to where the Intelligence service had established another perfectly innocent front. Dick tapped lightly at this door, and a key turned in the lock.

The man who stepped quickly back was one of the heads of the Civil Service. The man at the flat-topped desk was Colonel Stopford. The man on a chair beside him was one of the heads of the police force.


T

he Colonel, a big, elderly man, dressed in a grey sack suit, checked Dick's commencing salutation. "Never mind etiquette, Rennell," he said. "Sit down. You've heard about the man Von Kettler's escape last night, of course?"

"Yes, sir."

"It's known, then. We can't keep things dark. He vanished from his cell in the death house, three minutes before the time appointed for his execution, though, as a matter of fact, he wasn't going to be hanged. Apparently he walked through the walls.

"There's a sequel to it, Rennell. It seems he had told the assistant-superintendent, a man named Anstruther, that he'd meet him at a restaurant in town that night. He promised to leave him a memento. Anstruther happened to remember this boast of Von Kettler's, and he surrounded the restaurant with armed detectives, on the chance that the fellow would show up. Rennell, Von Kettler was there!"

"He went to this restaurant, sir?"

"He walked in, just before the place was surrounded, engaged a table, and ordered a sumptuous meal. He told the waiter his name, said he expected a friend to join him, walked into the wash-room—and vanished! Two minutes later Anstruther and his men were on the job. Von Kettler never came out of the wash-room, so far as anybody knows.

"In the midst of the hue and cry somebody pointed to the table that Von Kettler had engaged. There was a twenty-dollar bill upon it, and a scrap of paper reading: 'I've kept my word. Von K.'"

Colonel Stopford looked at Dick fixedly. "Rennell, we may be fools," he said, "but we realize what we're up against. It's a big thing, and we're going to need all our fighting grit to overcome it. You're one of the four men we're depending on. We're counting on you because of your record, and because of your degree in science at Heidelberg. The President wishes you to take charge of the whole Eastern Intelligence District, covering the entire south-eastern seaboard of the United States. You are to have complete freedom of action, and all civil, military, and naval officials have received instructions to co-operate with you."

"There goes Mrs. Wansleigh's ball," thought Dick, but he said nothing.


W

e're not the hunters, Dick Rennell," went on Colonel Stopford. "We're hiding under cover, and I'm counting on you to turn the tables. They even know my office is here. I had a long distance call from Savannah this morning in mocking vein. They advised me to have the White House watched to-night. I warned the President, and we've posted guards all round it."

"They held the wire while you called up the President?" asked Dick.

"Damn it, no! They called me up from Scranton the instant he'd finished speaking. They have the power of the devil, Rennell, with that infernal invisibility invention of theirs. Rennell, we're fighting unknown forces. Who this Invisible Emperor is, we don't even know. But one thing we've found out. He has his headquarters somewhere in your district. Somewhere along the south Atlantic seaboard. The greater part of his activities emanate from there. But we're fighting in the dark. The clue, the master clue that will enable us to locate him—that's what we lack."

The sun had set, it was beginning to grow dark. Colonel Stopford switched on the electric lamp beside his desk.

"What have you to say, Rennell?" he asked; and Dick was aware that the two other men were regarding him attentively.

"It's evident," said Dick, "that Von Kettler possessed this means of invisibility in his cell, and wasn't detected. He simply slipped out when the guard came to fetch him."

"Invisibility? Yes! But invisible's not the same thing as transparent," cried Stopford. "These folks have operated in broad daylight. They're transparent, damn them! Not even a shadow! You know what I mean, Rennell! What I'm thinking of! That crazy man you were in touch with six months ago, who prophesied this! We turned him down! He showed me a watch and said the salvation of the world was inside the case! I thought him insane!"


Y

ou mean Luke Evans, sir. That watch was his pocket model. He went off in a huff, saying the time would come when we'd want him and not be able to find him."

"But, damn him, he wanted to produce universal darkness, or some such nonsense, Rennell, and I told him that we wanted light, not darkness."

"It wasn't exactly that, sir." Colonel Stopford was a man of the old school: he had been an artillery officer in the Great War, and was characteristically impatient of new notions. Dick began carefully: "You'll remember, sir, old Evans claimed to have been the inventor of that shadow-breaking device that was stolen from him and sold in England."

"To a moving picture company!" snorted Stopford. "I asked him what moving pictures had to do with war."

"Evans was convinced that the invention would be applied to war. He claimed that it made the modern methods of military camouflage out of date completely. He said that by destroying shadows one could produce invisibility, since visibility consists in the refraction of wave lengths by material objects.

"When they stole his invention, he foresaw that it would be used in war. He set to work to nullify his own invention. He told me that he had unintentionally given to the enemies of the United States a means of bringing us to our knees, since he believed that British motion picture company was actually a subsidiary of Krupp's. He worked out a method of counteracting it."

"You must get him, Rennell. Even if it's all nonsense, we can't afford to let any chance go. If Evans's invention will counteract this damned invisibility business—"

The telephone on the Colonel's desk rang. He picked it up, and his face assumed an expression of incredulity. He looked about him, like a man bewildered. He beckoned to the police official, who hurried to his side, and thrust the receiver into his hand. The official listened.

"All right," he said. He turned to Dick and the Civil Service representative.

"Gentlemen," he said, "the President has disappeared from his office in the White House, and there are grave fears that he has been kidnapped!"

CHAPTER III

In the White House

C

olonel Stopford's car had been parked around the corner of the building, and within a minute the four men were inside it, Stopford at the wheel, and racing in the direction of the White House. A nod to the guard at the gate, and they were inside the grounds. At the entrance a single guard, in place of the four who should have been posted there, challenged sharply, and attempted to bar the way, not recognizing Dick or Stopford in their civilian clothes.

"Where's your officer?" demanded Stopford sharply.

Half-cowed by the Colonel's manner, the young recruit hesitated, and the four swept him out of the way and hurried on. The scene outside the main entrance to the White House was one of indescribable confusion. Soldiers were swarming in confused groups, some trying to force an entrance, others pouring out. Every moment civilians, streaming over the lawn, added to the number. Discipline seemed almost abandoned. From inside the building came outbursts of screams and cursing, the scuffling of a mob.

"Roscoe! Roscoe!" shouted Stopford. "Where's the President's secretary? Who's seen him? Let us pass immediately!"

No one paid the least attention to him. But a short, bare-headed civilian, who was struggling in the crowd, heard, and shouted in answer, waved his arms, and began to force his way toward the four. It was Roscoe, the secretary of President Hargreaves. The President was a childless widower, and Roscoe lived in the White House with him and was intimately in his confidence.

Roscoe gained Stopford's side. "Say—they've got him!" he panted. "They've got him somewhere—inside the building. They're trying to get him out! We've got to save him—but we can't see them—or him. They've made him invisible too, curse them! I heard him crying, 'Help me, Roscoe!' He saw me, I tell you—and I didn't know where he was!"


T

he little secretary was almost incoherent with fear and anger. The five men, forming a wedge, hurled themselves forward. Out of the White House entrance appeared a tall officer, revolver in hand. It was Colonel Simpson, of the President's staff. Half beside himself, he swept the weapon menacingly about him, shouting incoherently, and clearing a passage, into which the five hurled themselves.

Stopford seized his revolver hand, and after a brief struggle Simpson recognized him.

"He's in the building!" he shouted wildly. "Somewhere upstairs! I'm trying to form a cordon, but this damned mob's in the way. Kick those civilians out!" he cried to the soldiers. "Shoot them if they don't go! Guard the windows!"

Stopford and Dick, at the head of the wedge, pushed past into the White House. The interior was packed, men were struggling frantically on the staircase; it seemed hopeless to try to do anything.

Suddenly renewed yells sounded from above, a scream of anguish, howls of terror. There came a downward surge, then a forward and upward one, which carried the two men up the stairs and into the President's private apartments above.

In the large reception-room a mob was struggling at a window, beneath a blaze of electric light. A soldier was standing there like a statue, his face fixed with a leer of horror. In his hands was a rifle, with a blood-stained bayonet, dripping upon the hardwood floor at the edge of the rug. Upon the rug itself a stream of blood was spouting out of the air.

Dick looked at the sight and choked. There was something appalling in the sight: it was the quintessence of horror, that widening pool of blood, staining the rug, and flowing from an invisible body that writhed and twisted, while moans of anguish came from unseen lips.

Colonel Stopford leaped back, livid and staring. "God, it's got eyes—two eyes!" he shouted.

Dick saw them too. The eyes, which alone were visible, were about six inches from the floor, and they were appearing and disappearing, as they opened and shut alternately. It was a man lying there, a dying man, pierced by the soldier's bayonet by pure accident, dying and yet invisible.


T

he mob had scattered with shrieks of terror, but a few bolder spirits remained in a thin circle about that fearful thing on the rug. Dick bent over the man, and felt the outlines of the writhing body. It was a man, apparently dressed in some sort of uniform, but this was covered, from the top of the head to the feet, with a sort of sheer silken garment, bifurcating below the waist, and resembling a cocoon. It seemed to appear and alternately to vanish.

Dick seized the filmy stuff in his fingers, rent it, and stripped it away. Yells of terror and amazement broke from the throats of all. Instantly the thin circle of spectators had become reinforced by a struggling mass of men.

The half-visible cocoon clung to Dick's body like spider webs. But the man who had been wearing it had sprung instantly into view beneath the cluster of electric lights. He was a fair-haired young fellow of about thirty years, his features white and set in the agony of death.

He was dressed in a trim uniform of black, with silver braid, and on his shoulders were the insignia of a lieutenant. He opened his eyes, blue as the skies, and stared about him. He seemed to understand what had happened to him.

"Dogs!" he muttered.

Shrieks of fury answered him. The mob surged toward him as if to grind his face to pieces under their feet—and then recoiled, mouthing and gibbering. But it was at Dick that they were looking, not at the dying man.

He raised himself upon one elbow with a mighty effort. "His Majesty the Invisible Emperor! Long be his reign triumphant!" he chanted. It was his last credo. The words broke from his lips accompanied by a torrent of red foam. His head dropped back, his body slipped down; he was gone. And no one seemed to observe his passing. They were all screaming and gibbering at Dick.

"Rennell! Rennell!" yelled Stopford. "Where are you, Rennell? God, man, what's happened to your legs?"

Dick looked down at himself. For a moment he had the illusion that he was a head and a trunk, floating in the air. His lower limbs had become invisible, except for patches of trousering that seemed to drift through space. The mob in the room had fallen back gaping at him in horror.

Then Dick understood. It was the invisible garment that had coiled itself about him. He tore it from him and became visibly a man once more.

Shouts from another room! A surging movement of the crowd toward it. The muffled sounds of an automatic pistol, fitted with a silencer! Then screams:

"The devils are in there! They're murdering the soldiers!"

There followed a panic-stricken rush, more muffled firing, and then the sharp roar of rifles, and the fall of plaster. Some one was bawling the President's name. The rooms became a mass of milling human beings, lost to all self-control.

A bedlam of noise and struggle. Men fought with one another blindly, cursing soldiers fired promiscuously among the mob, riddling the walls, stabbing at the air. The plaster was falling in great chunks everywhere, filling the rooms with a heavy white cloud, in which all choked and struggled. The yells of the civilian mob below, struggling helplessly in the packed crowd that wedged the great stairway, made babel. Outside the White House a dense mob that filled the lawns was yelling back, and struggling to gain admittance. Suddenly the lights went out.

"They've cut the wires!" rose a wild, wailing voice. "The devils have cut the wires! Kill them! Kill everybody!"

His cry ended in a gurgle. Somewhere in that dark hell a struggle was going on, a well defined struggle, different from the random, aimless battling of the half-crazed soldiers and the civilians. President Hargreaves was still within the walls of the White House, it was known; it was physically impossible for him to have been carried away when every foot of space was packed. And through that darkness the invisible assailants were edging him, foot by foot, toward the outside.


D

ick was on the edge of this silent battle. He sensed it. Bracing himself against a bureau, while the mob surged past him, he tried to pierce the gloom, to reinforce with his perceptions what his instinct told him. A soldier, crazed with fear, came leaping at him, bayonet leveled. He thrust with a grunt. Dick avoided the glancing steel by a hand's breadth, and, as the impetus of the man's attack carried him forward, caught him beneath the chin with a stiff right-hand jolt that sent him sprawling.

From below the cries broke out again, with renewed violence: "They've got the President! Get them! Get them! Close all doors and windows!"

But a door went crashing down somewhere, to the tune of savage yells. The mob was pouring down the stairs. It was growing less packed above. Dick heard Stopford's voice calling his name.

"Here, sir" he shouted back, and the two men collided.

"For God's sake do what you can, Rennell!" shouted the Colonel. "They've got the President downstairs. They had him in this very room, in the thick of it all. I heard him cry out, as if under a gag. They put one of those damned cloths over him. God, Rennell, I'm going crazy!"

The upper floor of the White House was almost empty now. Dick thrust himself into the crowd that still jammed the stairs. He reached the ground floor. It was lighter here, but a glance showed him that it was impossible to attempt to restore any semblance of order. The big East Room was jammed with a fighting, cursing throng. Dick stumbled over the bodies of those who had fallen in the press, or had been shot down. Outside the mob was thickening, swarming through the grounds and screeching like madmen.


N

othing that could be done! Dick found himself caught once more in the human torrent. Presently he was wedged up against a broken window. He precipitated himself through the frame, dropped to the ground, stopped for an instant to catch breath.

The yelling mob was congregated about the main entrance of the White House, and on this side the grounds were comparatively empty. As Dick stopped, trying desperately to form some plan of action, he heard footsteps and low voices near him. Then two men came toward him, followed by three or four others.

The men—but, though the light was faint, Dick realized instantly that they were wearing invisible garments. He could see nothing of them; he could see through where they seemed to be—the trees, the buildings of the streets. Yet they were at his elbow. And they saw him. He heard one of them leap, and sprang aside as the butt of a pistol descended through the air and dropped where his head had been.

Yet no hand had seemed to hold it. It had been a pistol, reversed, and flashing downward, to be arrested in mid-air six inches from his face. But the men were not wholly invisible. Nearly six feet above the ground, three or four pairs of eyes were staring malevolently into Dick's. Only the eyes were there.

The two foremost men were breathing heavily. They were carrying something. Grotesquely through a rent in the invisible garment Dick saw a patch of trouser. He heard a muffled sigh. President Hargreaves, in the hands of his abductors!

Dick's actions were reflex. As the pistol hung beside his face, he snatched at it, wrested it away, struck with it, and heard a curse and felt the yielding impact of bone and flesh. He had missed the head but struck the shoulder. Next moment hands gripped the weapon, and a desperate struggle began.


I

t was torn from Dick's grasp. He struck out at random, and his fist collided with the chin of a substantial flesh and blood human being. Invisible arms grasped him. He fought free. The pistol slashed his face sidewise, the sight ripping a strip of flesh from the cheek. He was surrounded, he was being beaten down, though he was fighting gamely.

"Kill the swine! Shoot! Shoot!" Dick heard one of his assailants muttering.

Out of the void appeared the blue muzzle of another automatic, with a silencer on it. Dick ducked as a flame spurted from it. He felt the bullet stir his hair. He grasped at the hand that held it, and missed. Then he was held fast, and the muzzle swung implacably toward his head again. Helpless, he watched it describe that arc of death. It was only later that he wondered why he had fought all the while in silence, instead of crying for help.

But of a sudden the pistol was dashed aside. A woman's voice spoke peremptorily, in some language Dick did not understand. And he saw her eyes among the eyes that glared at him. Dark eyes that he knew, even if the voice had not revealed her identity. The eyes and voice of Fredegonde Valmy!

Dick cried her name. He put forth all his strength in a final struggle. Suddenly he felt a stunning impact on the back of the head. He slipped, reeled, threw out his hands, and sank down unconscious on the grass at the side of the path.

CHAPTER IV

The Invisible Ambassador

F

redegonde Valmy implicated in the conspiracy! That was the first thought that flashed into Dick's mind as he recovered consciousness. He might have suspected it! But the idea that the girl he loved was bound up with the murderous gang that was attacking the very foundations of civilization chilled him to the soul.

Dick had been picked up a few minutes after he had been struck down, identified by Colonel Stopford as he was about to be removed to a hospital, and carried into the White House. Order had been restored by the arrival of a detachment of troops from Fort Myers, the severed cables located and mended, and by midnight the interior of the Presidential home had been made habitable again.

President Hargreaves was gone—kidnapped despite the utmost efforts to protect him; and it was impossible to conceal that fact from the world. But the wheels of government still revolved. All night an emergency council sat in the White House, and, deciding that in a time of such grave danger heroic means must be adopted, with the consent of such of the Congressional leaders as could be summoned, a Council of Defence was organized.

The whole country east of the Mississippi was placed under martial law. The fleet and army were put on a war footing. Flights of airplanes were assembled at numerous points along the eastern seaboard. To this Council Donald was attached as head of Intelligence for the Eastern Division. Yet all this availed little unless the location of the Invisible Empire could be ascertained, and, despite telegraphic reports that came in hourly, alleging to have discovered its headquarters, nothing had been achieved in this direction.


T

he garment taken from the slain soldier had been examined by a half-dozen of the leading chemists of the East. Pending the arrival from New York of the celebrated Professor Hosmeyer, it was deposited under military guard in a dark closet. The result was unfortunate. The garment exhibited to the assembled scientists was a mere bifurcated silken bag.

The gas with which it had been impregnated, though it had been heavy enough to adhere to the fabric for hours, had also been volatile enough to have disappeared completely, leaving a residue which was identified as a magnesium isotope.

Equally spectacular had been the disappearance of Mademoiselle Fredegonde Valmy. A cable from the Slovakian Ambassador had arrived a few hours later, denying her authenticity. And with her disappearance came the discovery that she had been at the head of an espionage system with ramifications in every state department, and in every statesman's home.

Three days passed with no sign from the enemy. The Council sat all day. In the executive offices of the White House Dick toiled ceaselessly, planning, receiving reports, organizing the flights of airplanes at strategic points throughout his district. From time to time he would be summoned to the Council. At night he threw himself upon a cot in his office and slept a sleep broken by the constant arrival of messengers. And still there was no clue to the location of the headquarters of the marauders.

But in those three days there had been no sign of them. Hope had succeeded despair; in the rebound of confidence the populace was beginning to ridicule the nation-wide precautions against what were coming to be considered merely a gang of super-criminals. It was even whispered that President Hargreaves had not been kidnapped at all. The Freemen's Party accused the Government of a plot to subvert popular liberties.


D

ick received a summons on the third evening. Utterly worn out with his work, he pulled himself together and made his way into the Blue Room, where the Council was assembled. Vice-president Tomlinson, an elderly man, was in the chair. A non-entity, pushed into a post it had been thought he would adorn innocuously, he had been overwhelmed by his succession to the chief office of State.

Tomlinson did not like Dick, or any of the hustling younger officers who, unlike himself, realized the real significance of the danger that overhung the country. He sat pompously in his leather chair, regarding Dick as he entered in obedience to the summons.

"Well, Captain Rennell, what have you to report to us this evening?" he inquired, as Dick saluted and stood to attention at the table.

"We're improving our concentrations, Mr. Vice-president. We've eight flights of seaplanes scouring the coast in the hope of locating the stronghold of the Invisible Emperor. We've—"

"I'm sick and tired of that title," shouted Tomlinson. He sprang to his feet, his face flushed with anger. His nerves had broken under the continuous strain. "I'll give you my opinion, Captain Rennell," he said. "And that is that this so-called Invisible Emperor is a myth.

"A gang of thieves has invented a paint that renders them inconspicuous, has created a panic, and is taking advantage of it to terrorize the country. The whole business is poppycock, in my opinion, and the sooner this bubble bursts the better. Well, sir, what have you to say to that?"

"Have you ever seen any of these men in their invisible clothing, if I may ask, Mr. Vice-president?" inquired Dick, trying to keep down his anger. His nerves, too, were badly frazzled.

"No, sir, I have not, but my opinion is that this story is grossly exaggerated, and that the persons responsible are the reporters of our sensational press!" thundered Tomlinson.


H

e looked about him, a weak man proud of having asserted his authority. Somebody laughed.

Tomlinson glared at Dick, his rubicund visage purpling. But it was not Dick who had laughed. Nor any one at the council table.

That laugh had come from the wall beside the door. Again it broke forth, high-pitched, cold, derisive. All heads turned as if upon pivots to see who had uttered it.

"Good God!" exclaimed Secretary Norris, of the War Department, and slumped in his chair.

Five feet eight inches from the floor a pair of grey eyes looked at the Council members out of emptiness. Grey eyes, a man's eyes, cool, contemptuous, and filled with authority, with a contemptuous sense of superiority that left every man there dumb.

Dick was the first to recover himself. He stepped forward, not to where the invisible man was standing, but to a point between him and the door.

That cold laugh broke forth again. "Gentlemen, I am an ambassador from my sovereign, who chooses to be known as the Invisible Emperor," came the words. "As such, I claim immunity. Not that I greatly care, should you wish to violate the laws of nations and put me to death. But, believe me, in such case the retribution will be a terrible one."

Suddenly the envoy peeled off the gas-impregnated garments that covered him. He stood before the Council, a fair-haired young man, clad in the same fashion of trim black uniform as the bayonetted soldier had worn upstairs three nights before.

He bowed disdainfully, and it was Tomlinson who shouted:

"Arrest that man! I know his face! I've seen it in the papers. He's Von Kettler, the murderer who escaped from jail in an invisible suit."

"Oh, come, Mr. Vice-president," laughed Von Kettler, "are you sure this isn't all very much exaggerated?"

Tomlinson sank back in his chair, his ruddy face covered with sweat. Dick stared at Von Kettler. A suspicion was forming in his mind. He had seen eyes like those before, dark instead of grey, and yet with the same look of pride and breeding in them; the look of the face, too, impossible to mistake—he knew!

Fredegonde Valmy was Von Kettler's sister!


W

ell, gentlemen, am I to receive the courtesies of an ambassador?" inquired Van Kettler, advancing.

"You shall have the privileges of the gallows rope!" shouted Tomlinson. "Arrest that man at once, Captain Rennell!"

"Pardon me, Mr. Vice-president," suggested the Secretary for the Navy blandly, "but perhaps it would be more desirable to hear what he has to say."

"Immunity for thieves, robbers, murderers!"

"Might I suggest," said Von Kettler suavely, "that, since the United States has honored my master by placing itself upon a war footing, it has accorded him the rights of a belligerent?"

"We'll hear you, Mr. Von Kettler," said the Secretary of State, glancing along the table. Three or four nodded, two shook their heads: Tomlinson only glared speechlessly at the intruder. Von Kettler advanced to the table and laid a paper upon it.

"You recognize that signature, gentlemen?" he asked.

At the bottom of the paper Dick saw scrawled the bold and unmistakable signature of President Hargreaves.

"An order signed by the President of your country," purred Von Kettler, "ordering your military forces replaced upon a peace footing, and the acceptance of our conditions. They are not onerous, and will not interfere with the daily life of the country. Merely a little change in that outworn document, the Constitution. My master rules America henceforward."

Somebody laughed: another laughed: but it was the Secretary of State who did the fine thing. He took up the paper bearing what purported to be President Hargreaves's signature, and tore it in two.

"The people of this country are her rulers," he said, "not an old man dragooned into signing a proclamation while in captivity—if indeed that is President Hargreaves's signature."


T

here came a sudden burst of applause. Von Kettler's face became the mask of a savage beast. He shook his fist furiously.

"You call my master a forger?" he shouted. "You yourselves repudiate your own Constitution, which places the control of army and navy in the hands of your President? You refuse to honor his signature?"

"Listen to me, Mr. Von Kettler!" The voice of the Secretary of State cut like a steel edge. "You totally mistake the temper of the people of this country. We don't surrender, even to worthy adversaries, much less to a gang of common thieves, murderers, and criminals like yourselves. You have been accorded the privilege you sought, that of an envoy, and that was straining the point. Show yourself here again after two minutes have elapsed, and you'll go to the gallows—for keeps."

"Dogs!" shouted Von Kettler, beside himself with fury. "Your doom is upon you even at this moment. I have but to wave my arm, and Washington shall be destroyed, and with her a score of other cities. I tell you you are at our mercy. Thousands of lives shall pay for this insult to my master. I warn you, such a catastrophe is coming as shall show you the Invisible Emperor does not threaten in vain!"

With complete nonchalance the Secretary of State took out his watch. "One minute and fifteen seconds remaining. Captain Rennell," he said. "At the expiration of that time, put Mr. Von Kettler under arrest. I advise you to go back to your master quickly, Mr. Von Kettler," he added, "and tell him that we'll have no dealings with him, now or ever."


F

or a moment longer Von Kettler stood glaring; then, with a laugh of derision and a gesture of the hands he vanished from view. And, though they might have expected that denouement, the members of the Council leaped to their feet, staring incredulously at the place where he had been. Nothing of Von Kettler was visible, not even the eyes, and there sounded not the slightest footfall.

Dick sprang forward to the door, but his outstretched arms encountered only emptiness. In spite of the Secretary of State's instructions, he was almost minded to apprehend the man. If he could get him!

The corridor was empty. A guard of soldiers was at the entrance, but they did not block the entrance. Even now Von Kettler might be passing them! Why didn't his feet sound upon the floor? How could a bulky man glide so smoothly?

Perhaps because Dick was undecided what to do, Von Kettler escaped him. By the time he reached the guards he knew he had escaped. Suddenly there came an unexpected denouement. Somewhere on the White House lawn a guard challenged, fired. The snap of one of the silenced automatics answered him.

When Dick and the guards reached the spot, the man was lying in a crumpled heap.

"An airplane," he gasped. "Invisible airplane. I—bumped into it. Men—in it. The damned dogs!"

He died. Dick stared around him. There was no sign of any airplane on the lawn, nothing but the tents of the guards, white in the moonlight, and the grim array of anti-aircraft guns that Dick had placed there.

But behind the White House, in hastily constructed hangars, were a half-dozen of the latest pursuit airships—beautiful slim hulls, heavily armored, with armored turrets containing each a quick-firer with the new armor-piercing bullets. One of these ships, Dick's own, was kept perpetually warmed and ready to take the air.


D

ick raced across the lawn, yelled to the startled guard in charge. The mechanics came running from their quarters. Almost by the time Dick reached it the ship was ready.

He twirled the helicopter starter, and she roared and zoomed, taking an angle of a hundred and twenty-five degrees upward off a runway of twenty yards. Into the air she soared, into the moonlight, up like an arrow for five hundred feet.

Dick pulled the soaring lever, and she hung there, buzzing like a bee as her helicopters, counteracting the pull of gravity, held her comparatively stable. He scanned the air all about him.

Washington lay below, her myriad lights gleaming. Immediately beneath him Dick saw the guns and the tents of the soldiers, and the little group that was removing the body of the murdered soldier on a stretcher. But there were no signs of any hostile craft.

Had the murdered man really bumped into an invisible airship, or had he only thought he had? Had those devils learned to apply the gas to the surfaces of airplanes? There was no reason why they should not have done so.

But surely the utmost ingenuity of man had not contrived to render a modern plane, with its metalwork and machinery, absolutely transparent?


A

nd, again, how was it possible to have silenced the sound of engines, the whir of a propeller, so that there should be no auditory indication whatever of a plane's presence?

Dick looked all about him. Nothing was in the air—he could have sworn it. He replaced the soaring lever and banked in a close circle, his glance piercing the night. No, there was nothing.

Crash! Boom! The plane rocked violently, tossing upon gusts of air. A huge, gaping hole of blackness had suddenly appeared in the middle of the White House lawn. The tents were flat upon the ground. Through the rising smoke clouds Dick saw tongues of flame.

No shell that, but a bomb, and dropped from the skies less than five hundred feet from where Dick hovered. Yet there was nothing visible in the skies save the round orb of the moon.

A rush of wind past Dick's face! One of the vanes of the helicopter crumpled and fluttered away into the night. Dick needed no further persuasion. The dead soldier had not lied.

Von Kettler had begun the fulfillment of his threat!

CHAPTER V

The Enemy Strikes

A

s Dick's airship veered and side-slipped, he kicked hard on the left rudder and brought the nose around. Furiously he sprayed the air with a leaden hail from his quick-firer. He heard a rush of wind go past him, and realized that his unseen antagonist had all but rammed him.

Yet nothing was visible at all, save the moon and the empty sky. He had heard the rush of the prop-wash, but he had seen nothing, heard nothing else. Incredible as it seemed, the pilot was flying a plane that had attained not merely invisibility but complete absence of all sound.

Dick side-slipped down, pancaked, and crashed. He emerged from a plane wrecked beyond hope of early repair, yet luckily with no injury beyond a few minor bruises. He rushed toward the hangar, to encounter a bevy of scared mechanics.

"Another plane! Rev one up quick!" he shouted.

Planes were already being wheeled out, pilots in flying suits and goggles were striding beside them. Dick ordered one of them away, stepped into his plane, and in a moment was in the air again.

In the minute or two that had elapsed since the encounter, the enemy had been active. Crash after crash was resounding from various parts of Washington. Buildings were rocking and toppling, débris strewed the streets, fires were springing up everywhere. A thousand feet aloft, Dick could see the holocaust of destruction that was being wrought by the infernal missiles.

Bombs of such power had been the unattained ambition of every government of the world—and it had been left to the men of the Invisible Emperor to attain to them. Whole streets went into ruin at each discharge and from everywhere within the city the wailing cry of the injured went up, in a resonant moan of pain.

In the central part of the city, the district about F Street and the government buildings, nothing was standing, except those buildings fashioned of structural steel, and these showed twisted girders like the skeletons of primeval monsters, supporting sections of sagging floors. Houses, hotels had melted into shapeless heaps of rubble, which filled the streets to a depth of a dozen yards, burying everything beneath them. Yet here and there could be seen the forms of dead pedestrians, motor-cars emerging out of the débris, lying in every conceivable position; horses, horribly mangled, were shrieking as they tried to free themselves. And yet, despite this ruin, the general impression upon Dick's mind, as he beat to and fro, signaling to his flight to spread, was that of a vast, empty desolation.


F

urther away: where the ruin had not yet fallen, thousands of human beings were milling in a mass, those upon the fringes of the crowd perpetually breaking away, other swarms approaching them, so that the entire agglomeration resembled a seething whirlpool turning slowly upon itself.

Then of a sudden the strains of the national anthem floated up to Dick's ears. A band was playing in the White House grounds. The tune was ragged, and the drum came in a fraction of a second late, but an immense pride and elation filled Dick's soul.

"They'll never beat us!" he thought, intensely, "with such a spirit as that!"

He had signaled his flight to spread, and search the air. He could see the individual ships darting here and there over the immensity of the city, but none knew better than he how fruitless their effort was. And the marauders had not ceased their deadly work.

A bomb dropped near the Washington Monument, sending up a huge spout of dust that veiled it from his eyes. Instinctively Dick shot toward the scene. Slowly the dust subsided, and then a yell of exultation broke from Dick's lips. The noble shaft still stood, a slim taper pointing to the skies.

It was an omen of ultimate success, and Dick took heart. No, they'd never beat the grim, unconquerable tenacity of the American people.

Yet the damage was proceeding at a frightful rate. A bomb dropped squarely on the Corcoran Gallery and resolved it into a heap of silly stones. A bomb fell in the middle of Pennsylvania Avenue, and the houses on either side collapsed like houses of cards, falling into a sulphurous, fiery pit. And still there was nothing visible but the sky and the moon.


D

ick gritted his teeth and swore as he circled over the site of destruction, out of which tiny figures were struggling. He heard the clang of the fire bells as the motor trucks came roaring toward the scene. Then crash! again. Five blocks northward another dense cloud of dust arose, and the new area of destruction, spreading as swiftly as ripples over a pond, joined the former one, leaving a huge, irregular open space, piled up with masonry and brick in a number of flat-topped pyramids.

Into this, houses went crashing every moment, with a sound like the clatter of falling crockery, but infinitely magnified.

"The devils! The swine!" shouted Dick. "And we gave Von Kettler the privileges of an ambassador!"

And Fredegonde was the sister of this devil! The remembrance of that struck a cold chill to Dick's heart again. He tried to blot out her picture from his mind, but he still saw her as she had appeared that day after the air ride, flushed, smiling, radiant in her dark beauty.

A murderess and a spy! He cursed her as he banked and circled back. He was helpless. He could do nothing. And all Washington would be destroyed by morning, if the supply of bombs kept up. But there was more to come. Suddenly Dick became aware that two of his flight, at widely separated distances, were going down in flames. Flaming comets, they dropped plump into the destruction below. Another caught fire and was going down. No need to question what was happening.

The invisible enemy was attacking his flight and picking off his men one by one!

He drove furiously toward two of his planes whose erratic movements showed that they were being attacked. As he neared them he saw one catch fire and begin its earthward swoop. Then the fuselage crackled beside him, and his instrument board dissolved into ruin. Instinctively he went round in a tight bank and loosed his machine-gun. Nothing there! Nothing at all! Yet his right wing went ragged, and his own furious blasts into the sky, their echoes drowned by the roar of his propeller, were productive of nothing.


H

e shot past the uninjured plane, signalling it to descend. He wasn't going to let his men ride aloft to helpless butchery. Nothing could be done until some means was discovered of counteracting the enemy's terrific advantage.

He darted across the heart of the city to where another of the flight was circling, waggling his wings to indicate to it to descend. Then on to the next plane and the next, shepherding them. Thank God they understood! They were bunching toward the hangar. Yet another took fire and dropped, a burning wreck. Half his flight out of commission, and not an enemy visible!

He was aloft alone now, courting death—instant, invisible death. He wouldn't descend until that carnival of murder was at an end. But it was not at an end. Another crash, far up Pennsylvania Avenue, showed an attempt upon the Capitol. Again—again, and a smoking hell wreathed the noble buildings so that it was no longer possible to see them. A lull, and then a crash nearer the city's heart. Crash! Crash!

Invisible though the enemy was, it was easy to trace the movements of this particular plane by the successive areas of destruction that it left behind it. It was coming back over Pennsylvania Avenue, dropping its bombs at intervals. It was methodically wiping out an entire section of Washington.

Dick drove his plane toward it. There was one chance in a thousand that, if he could accurately gauge the progress of his invisible antagonist, he could crash him and go down with him to death. If he could get close enough to feel his prop-wash! A wild chance, but Dick's mind was keyed up to desperation. He shot like an arrow toward the scene, with a view to intercepting the murderer.

Then of a sudden he became aware of a curious phenomenon. A black beam was shooting across the sky. A black searchlight! It came from the flat top of a large hotel that had somehow escaped the universal destruction, and, with its gaunt skeleton of structural steel showing in squares, towered out of the ruin all about it like an island.


I

t was from here that the black beam started. It spread fanwise across the sky. But it was not merely blackness. It was utter and impenetrable darkness, cleaving the sky like a knife. Where it passed, the rays of the moon were extinguished as fire is extinguished by water.

A beam of absolute blackness, that pierced the air like a widening cone, and made the night seem, by contrast, of dazzling brightness along either dark border.

High into the air that dark beam shot, moving to and fro in the sky. Dick, darting toward the spot where he hoped to find his invisible enemy, found himself caught in it.

In utter, inextinguishable darkness! Like a trapped bird he fluttered, hurling himself this way and that till suddenly he found himself blinking in the dazzling light of the moon again, and the black beam was overhead.

Crash! Another widening sphere of ruin as the invisible marauder dropped a bomb. Dick cursed bitterly. Trapped in that black beam, he had lost his direction. The invisible plane had shot past the point where he had hoped to intercept it.

He flung his soaring lever, and hung suspended in the air. An easy mark for the enemy, if he chose to take the opportunity. No matter. Death was all that Dick craved. He had seen half his flight wiped out, and a hundred thousand human beings hurled to destruction. He wanted to die.

Then suddenly a wild shout came to his ears, as if all Washington had gone mad with triumph. And Dick heard himself shouting too, before he knew it, almost before he knew why.


F

or overhead, where the inky finger searched the sky, a luminous shape appeared, a silvery cigar, riding in the void. The finger missed it, and again there was only the moonlight. It caught it again—and again the whole devastated city rang with yells of derision, hate, and anger as the black beam held it.

It held it! To and fro that silvery cigar scurried in a frantic attempt to avoid detection, and remorselessly the black beam held it down.

It held it down, and it outlined it as clearly as a figure on the moving picture screen. Then suddenly there came a flash, followed by a dull detonation, and a black cloud appeared, spreading into a flower of death near the cigar, and at the edge of the black beam. The cheers grew frantic. The anti-aircraft battery in the White House grounds had grasped the situation, and was opening fire.

To and fro, like a trapped beast, the cigar-shaped airplane fled. Once it seemed to escape. It faded from the edge of the black finger—faded into nothingness amid a roar of execretion. Then it was caught and held.

Truncated, bounded by an arc of sky, the black finger followed the murderer in his flight remorselessly. And all around him the anti-aircraft guns were placing a barrage of death.

He was trapped. No need for Dick to rush in to battle. To do so might call off that deadly barrage that held the murderer in a ring of death. Hovering, Dick watched. And then, perhaps panic-stricken, perhaps rendered desperate, perhaps through sheer, wanton courage that might have commanded admiration under nobler circumstances, the airship turned and drove straight in the direction of the battery, dropping another bomb as she did so.


I

t fell in a crowded street, swarming with spectators who had clambered upon the fallen débris, and it wrought hideous destruction. But this time there was hardly a cry—no unison of despair such as had come to Dick's ears before. The suspense was too tense. All eyes watched the airship as, seeming to bear a charmed life, she drove for the White House itself, through a ring of shells that widened and contracted alternately, with the object of placing a last bomb squarely upon the building before going down in death. And all the while the black searchlight held it.

Dick Rennell was to experience many thrilling moments afterward, but there was never a period, measurable by seconds, yet seeming to extend through all eternity—never a period quite so fraught with suspense as, hovering there, he watched the flight of that silvery plane speeding straight toward the executive mansion while all around it the shells bloomed and spread. It was over the White House grounds. The archies had failed; they were being outmaneuvered, they could not be swung in time to follow the trajectory of the plane. Dick held his breath.

Then suddenly the silvery ship dissolved in a blaze of fire, a shower of golden sparks such as fly from a rocket, and simultaneously the last bomb that she was to drop broke upon the ground below.

Down she plunged, instantly invisible as she escaped the finger of the black beam; but she dropped into the vortex of ruin that she herself had created. Into a pit of blazing fire, criss-crossed by falling trees, that had engulfed the battery and a score of men.

Then suddenly Dick understood. He flung home the soaring lever, banked, and headed, not for the White House, but for the flat roof of the hotel from which the black searchlight was still projecting itself through the skies. He hovered above, and dropped, light as a feather, upon the rooftop.


T

here was only one person there—an old man dressed in a shabby suit, kneeling before a great block of stone that had been dislodged upward from the parapet and formed a sort of table. Upon this table the old man had placed a large, square box, resembling an exaggerated kodak, and it was from the lens of this box that the black beam was projecting.

Dick sprang from his cockpit as the old man rose in alarm. He ran to him and caught him by the arm.

"Luke Evans!" he cried. "Thank God you've come back in time to save America!"

CHAPTER VI

The Gas

I

n the Blue Room of the White House the Council listened to old Luke Evans's exposition of his invention with feelings ranging from incredulity to hope.

"I've been at work all the time," said the old man, "not far from here. I knew the day would come when you'd need me. I put my pride aside for the sake of my country."

"Tell us in a few words about this discovery of yours, Mr. Evans," said Colonel Stopford.

Luke Evans placed the square black case upon the table. "It's simple, like all big things, sir," he answered. "The original shadow-breaking device that I invented was a heavy, inert gas, invisible, but almost as viscous as paint. Applied to textiles, to inorganic matter, to animal bodies, it adheres for hours. Its property is to render such substances invisible by absorbing all the visible light rays that fall upon it, from red to violet. Light passes through all substances that are coated with this paint as if they did not exist."

"And this antidote of yours?" asked Colonel Stopford.

"Darkness," replied Luke Evans. "A beam of darkness that means absolute invisibility. It can be shot from this apparatus"—he indicated the box upon the table. "This box contains a minute portion of a gas which exists in nature in the form of a black, crystalline powder. The peculiar property of this powder is that it is the solidified form of a gas more volatile than any that is known. So volatile is it that, when the ordinary atmospheric pressure of fifteen pounds to the square inch is removed, the powder instantly changes to the gaseous condition."

"By pressing this lever"—Evans pointed at the box—"a vacuum is created. Instantly the powder becomes a gas, which shoots forth through this aperture with the speed of a projectile, taking the form of a beam of absolute blackness. Or it can be discharged from cylinders in such a way as to extend over a large area within a few minutes."

"But how does this darkness make the invisible airships luminous?" asked Stopford. "Why does not your darkness destroy all light?"

"In this way, sir," replied the old inventor. "The shadow-breaking gas with which the airships are painted confers invisibility because it absorbs sunlight. But it does not absorb the still more rapid waves, or oscillations which manifest themselves as radio-activity. On the contrary, it gathers and reflects these.

"Now Roentgen, the discoverer of the X-ray, observed that if X-rays are allowed to enter the eye of an observer who is in complete darkness, the retina receives a stimulus, and light is perceived, due to the fluorescent action of the X-rays upon the eyeball.

"Consequently, by creating a beam of complete darkness, I bring into clear visibility the fluorescent gas that coats the airships; in other words, the airships become visible."

"If a light ray is nullified upon entering the field of darkness, will it emerge at the other edge as a perfect light ray again?" asked Stopford.

"It will emerge unchanged, since the black beam destroys light by slightly slowing down the vibrations to a point where they are not perceived as light by the human eye. On emerging from the beam, however, these vibrations immediately resume their natural frequency. To give you a homely parallel, the telephone changes sound waves to electric waves, and re-converts them into sound waves at the other end, without any appreciable interruption."

"Then," said Stopford, "the logical application of your method is to plunge every city in the land into darkness by means of this gas?"

"That is so, sir, and then we shall have the advantage of invisibility, and the enemy ships will be in fluorescence."

"Damned impracticable!" muttered Stopford.

"You seriously propose to darken the greater part of eastern North America?" asked the Secretary for War.

"The gas can be produced in large quantities from coal tar besides existing in crystalline deposits," replied Luke Evans. "It is so volatile that I estimate that a single ton will darken all eastern North America for five days. Whereas the concentration would be made only in specific areas liable to attack. The gas is distilled with great facility from one of the tri-phenyl-carbinol coal-tar derivatives."

Vice-president Tomlinson was a pompous, irascible old man, but it was he who hit the nail on the head.

"That's all very well as an emergency measure, but we've got to find the haunt of that gang and smash it!"

An orderly brought in a telegraphic dispatch and handed it to him. The Vice-president opened it, glanced through it, and tried to hand it to the Secretary of State. Instead, it fluttered from his nerveless fingers, and he sank back with a groan. The Secretary picked it up and glanced at it.

"Gentlemen," he said, trying to control his voice, "New York was bombed out of the blue at sunrise this morning, and the whole lower part of the city is a heap of ruins."


I

n the days that followed it became clear that all the resources of America would be needed to cope with the Invisible Empire. Not a day passed without some blow being struck. Boston, Charleston, Baltimore, Pittsburg in turn were devastated. Three cruisers and a score of minor craft were sunk in the harbor of Newport News, where they were concentrating, and thenceforward the fleet became a fugitive force, seeking concealment rather than an offensive. Trans-Atlantic sea-traffic ceased.

Meanwhile the black gas was being hurriedly manufactured. From cylinders placed in central positions in a score of cities it was discharged continuously, covering these centers with an impenetrable pall of night that no light would penetrate. Only by the glow of radium paint, which commanded fabulous prices, could official business be transacted, and that only to a very small degree.

Courts were closed, business suspended, prisoners released, perforce, from jails. Famine ruled. The remedy was proving worse than the disease. Within a week the use of the dark gas had had to be discontinued. And a temporary suspension of the raids served only to accentuate the general terror.

There were food riots everywhere, demands that the Government come to terms, and counter-demands that the war be fought out to the bitter end.

Fought out, when everything was disorganized? Stocks of food congested all the terminals, mobs rioted and battled and plundered all through the east.

"It means surrender," was voiced at the Council meeting by one of the members. And nobody answered him.

Three days of respite, then, instead of bombs, proclamations fluttering down from a cloudless sky. Unless the white flag of surrender was hoisted from the summit of the battered Capitol, the Invisible Emperor would strike such a blow as should bring America to her knees!


I

t was a twelve-hour ultimatum, and before three hours had passed thousands of citizens had taken possession of the Capitol and filled all the approaches. Over their heads floated banners—the Stars and Stripes, and, blazoned across them the words, "No Surrender."

It was a spontaneous uprising of the people of Washington. Hungry, homeless in the sharpening autumn weather, and nearly all bereft of members of their families, too often of the breadwinner, now lying deep beneath the rubble that littered the streets, they had gathered in their thousands to protest against any attempt to yield.

Dick, flying overhead at the apex of his squadron, felt his heart swell with elation as he watched the orderly crowds. This was at three in the afternoon: at six the ultimatum ended, the new frightfulness was to begin.

At five, Vice-president Tomlinson was to address the crowds. The old man had risen to the occasion. He had cast off his pompousness and vanity, and was known to favor war to the bitter end. Dick and his squadron circled above the broken dome as the car that carried the Vice-president and the secretaries of State and for War approached along the Avenue.

Rat-tat, rat-a-tat-tat!

Out of the blue sky streams of lead were poured into the assembled multitudes. Instantly they had become converted into a panic-stricken mob, turning this way and that.

Rat-a-tat-tat. Swaths of dead and dying men rolled in the dust, and, as wheat falls under the reaper's blade, the mob melted away in lines and by battalions. Within thirty seconds the whole terrain was piled with dead and dying.

"My God, it's massacre! It's murder!" shouted Dick.


T

hey had not even waited for the twelve hours to expire. To and fro the invisible airplanes shot through the blue evening sky, till the last fugitives were streaming away in all directions like hunted deer, and the dead lay piled in ghastly heaps everywhere.

Out of these heaps wounded and dying men would stagger to their feet to shake their fists impotently at their murderers.

In vain Dick and his squadron strove to dash themselves into the invisible airships. The pilots eluded them with ease, sometimes sending a contemptuous round of machine-gun bullets in their direction, but not troubling to shoot them down.

Two small boys, carrying a huge banner with "No Surrender" across it, were walking off the ghastly field. Twelve or fourteen years old at most, they disdained to run. They were singing, singing the National Anthem, though their voices were inaudible through the turmoil.

Rat-tat! Rat-tat-a-tat! The fiends above loosed a storm of lead upon them. Both fell. One rose, still clutching the banner in his hand and waved it aloft. In a sudden silence his childish treble could be heard:

My country, 'tis of thee
Sweet land of lib-er-ty—

The guns rattled again. Clutching the blood-stained banner, he dropped across the body of his companion.

Suddenly a broad band of black soared upward from the earth. Those in charge of the cylinders placed about the Capitol had released the gas.

A band of darkness, rising into the blue, cutting off the earth, making the summit of the ruined Capitol a floating dome. But, fast as it rose, the invisible airships rose faster above it.

A last vicious volley! Two of Dick's flight crashing down upon the piles of dead men underneath! And nothing was visible, though the darkness rose till it obliterated the blue above.


A

t dawn the Council sat, after an all-night meeting. Vice-president Tomlinson, one arm shattered by a machine-gun bullet, still occupied the chair at the head of the table.

Outside, immediately about the White House, there was not a sound. Washington might have been a city of the dead. The railroad terminals, however, were occupied by a mob of people, busily looting. There was great disorder. Organized government had simply disappeared.

Each man was occupied only with obtaining as much food as he could carry, and taking his family into rural districts where the Terror would not be likely to pursue. All the roads leading out of Washington—into Virginia, into Maryland, were congested with columns of fugitives that stretched for miles.

Some, who were fortunate enough to possess automobiles, and—what was rarer—a few gallons of gas, were trying to force their way through the masses ahead of them; here and there a family trudged beside a pack-horse, or a big dog drew an improvised sled on wheels, loaded with flour, bacon, blankets, pillows. Old men and young children trudged on uncomplaining.

The telegraph wires were still, for the most part, working. All the world knew what was happening. From all the big cities of the East a similar exodus was proceeding. There was little bitterness and little disorder.

It was not the airship raids from which these crowds were fleeing. Something grimmer was happening. The murderous attack upon the populace about the Capitol had been merely an incident. This later development was the fulfilment of the Invisible Emperor's ultimatum.

Death was afield, death, invisible, instantaneous, and inevitable. Death blown on the winds, in the form of the deadliest of unknown gases.


I

n the Blue Room of the White House a score of experts had gathered. Dick, too, with the chiefs of his staff, Stopford, and the army and naval heads. Among them was the chief of the Meteorological Bureau, and it was to him primarily that Tomlinson was reading a telegraphic dispatch from Wilmington, South Carolina:

"The Invisible Death has reached this point and is working havoc throughout the city, spreading from street to street. Men are dropping dead everywhere. A few have fled, but—"

The sudden ending of the dispatch was significant enough. Tomlinson picked up another dispatch from Columbia, in the same State:

"Invisible Death now circling city," he read. "Business section already invaded. All other telegraphists have left posts. Can't say how long—"

And this, too, ended in the same way. There were piles of such communications, and they had been coming in for eighteen hours. At that moment an orderly brought in a dozen more.

Tomlinson showed the head of the Meteorological Bureau the chart upon the table. "We've plotted out a map as the wires came in, Mr. Graves," he said. "The Invisible Death struck the southeast shore of the United States yesterday afternoon near Charleston. It has spread approximately at a steady rate. The wind velocity—?"

"Remains constant. Seventy miles an hour. Dying down a little," answered Graves.

"The death line now runs from Wilmington, South Carolina, straight to Augusta, Georgia," the Vice-president pursued. "Every living thing that this gas has encountered has been instantly destroyed. Men, cattle, birds, vermin, wild beasts. The gas is invisible and inodorous. These gentlemen believe it may be a form of hydrocyanic acid, but of a concentration beyond anything known to chemistry, so deadly that a billionth part of it to one of air must be fatal, otherwise it could not have traveled as it has done. Warnings have been broadcasted, but there are no stocks of chemicals that might counteract it. Flight is the only hope—flight at seventy miles an hour!"


H

is voice shook. "This gas has been loosed, as you told us, upon the wings of the hurricane that came through the Florida Strait. What are the chances of its reaching Washington?"

"Mr. Vice-president, if the wind continues, and this gas has sufficient concentration, it should be in Washington within the next eight hours." Graves replied. "If the wind changes direction, however, this gas will probably be blown out to sea, or into the Alleghanies, where it will probably be dissipated among the hills, or by the foliage on the mountains. I'm not a chemist—"

"No, sir, and I am not consulting you as one," answered old Tomlinson. "A death belt several hundred miles in length and three or four hundred deep has already been cut across this continent. We are faced with wholesale, unmitigated murder, on such a scale as was never known before. But we are an integral part of America, and Washington has no more right to expect immunity than our devastated Southern States. The question we wish to put to you is, can you trace the exact course taken by the hurricane?"

"I can, Mr. Vice-president," answered Graves. "It originated somewhere in the West Indian seas, like all these storms. We've been getting our reports almost as usual. Our first one came from Nassau, which was badly damaged. The storm missed the Florida coast, as many of them do, and struck the coast of South Carolina—in fact, we received a report from Charleston, which must have almost coincided with your first report of the gas."

"If the storm missed the Florida coast, it follows that the gas was not discharged from any point on the American continent," said Tomlinson. "From some point off Florida—from some island, or from a plane or from a ship at sea."

"Not from a ship at sea, Mr. Vice-president," interposed the head of the Chemical Bureau. "To discharge gas on such an extensive scale would require more space than could be furnished by the largest vessel, in my opinion."

"In all probability the gas was 'loaded,' so to say, onto the gale somewhere in the Bahamas," said Graves. "That seems to me the most likely explanation."


V

ice-president Tomlinson nodded, and picked up one of the latest telegraphic dispatches, as if absently.

"Gentlemen," he said, "the Invisible Death has already reached Charlotte."

He picked up another. "Reported Abaco Island, Bahamas, totally wrecked by storm. All communication has ceased," he read. He turned to Dick and spoke as if inspired. "Captain Rennell, there is your destination," he thundered. "They've betrayed themselves. We've got them now. You understand?"

"By God, sir! It's from Abaco Island, then, that those devils have been carrying on their game of wholesale murder!"

Suddenly a contagion of enthusiasm seemed to sweep the whole assemblage. Every man was upon his feet in an instant, white, quivering, lips opened for speech that trembled there and did not come.

It was Secretary Norris spoke. "The Vice-president has hit the mark," he said, with a dramatic gesture of his arm. "Yes, they've betrayed themselves. Their headquarters are on Abaco Island. It's one of the largest in the Bahamas." He turned to the Secretary for the Navy. "You can rush the fleet there, sir?" he asked.

"Within forty-eight hours I'll have every vessel that can float off Abaco Island."

"I'll concentrate all airplanes. Take your flight, Captain Rennell. We'll stamp out that nest of murderers if we blow Abaco Island to the bottom of the sea. It can be done!"

"It can be done, sir—with Luke Evans and his invention," answered Dick.

CHAPTER VII

On the Trail

T

hree hours later, about the time when the war council rose after completing its plans, a sudden shift of the wind blew the poison gas out to sea, just when it appeared certain that it would reach the capital of the nation.

The southern half of Virginia had been swept over. Operators, telegraph and telephone, staying at their posts had sent in constant messages that had terminated with an abruptness which told of the tragic sequel. Yet, at that distance from its source, the intensity of the gas had been to some extent dissipated.

Poisonous beyond any gas known, so deadly as to make hydrocyanic gas innocuous in comparison, still as it was swept northward on the wings of the wind, there had been an increasing number of non-fatal casualties. The most northernly point reached by the gas was Richmond, and here some fifty per cent of those stricken had suffered paralysis instead of death.

But a new element had been injected into the situation. Even the heroic courage shown by the populace in the beginning had had its limits. The morning after the news of the Invisible Death's advent was made public mobs had gathered in all the large cities of the East, demanding surrender.

The submerged elements of crime and disorder had come to the surface at last. Committees were formed, with the avowed object of yielding to the Invisible Emperor, and averting further disaster. In Washington, a city of the dead, half the members of Congress and the Senators had gathered in the ruined Capitol, to debate the situation.

There were rumors of an impending march on the White House, of a coup d'ètat.


T

he action of the Government was prompt. Five hundred loyalists were enrolled, armed, and posted round the White House: every avenue of approach was commanded by machine-guns. Meanwhile the news was spread by radio that the headquarters of the Invisible Emperor had been located, and that a strong bombing squadron was being dispatched to destroy it.

The entire fleet was to follow, and it was confidently anticipated that within a little while the Terror would be at an end.

Those at the white House were less sanguine. There was none but realized the diabolical strength of their antagonists.

"Everything depends upon the outcome of the next forty-eight hours, and everything depends on you, Rennell," said Secretary Norris to Dick, as he stood beside his plane. Behind him his flight of a dozen airships was drawn up.

"Find them," added the Secretary; "cover Abaco Island with the black gas, and the navy and the marines will wipe up the mess that you leave behind you. God help you—and all of us, Rennell!"

He gripped Dick's hand and turned away. Dick was very sober-minded as he climbed into his cockpit. He knew to the full how much depended upon himself and Luke Evans. Already the shouts of the insurgents were to be heard at the ends of the barriers, commanded by the machine-guns, and patrolled by the enlisted volunteers.

Negro mobs were building counter-barricades of their own with rubble from the fallen edifices. Civil war might be postponed for eight-and-forty hours, but after that unless there was news of victory, the whole structure of civilization would be smashed irreparably.

It was up to Dick and Luke Evans, and they had assumed such a responsibility as rarely falls to the lot of man in war.


D

ick was to lead the flight in a two-seater Barwell plane. This was one of the latest types, and had been hurriedly adapted to the purpose for which it was to be used. Dick himself occupied the rear seat, with its dual controls, and the gun in its armored casing. In front sat old Luke Evans, in charge of the black gas projector.

His famous camera box, containing a minute quantity of gas in slow combustion, and projecting the black searchlight, had been built into the plane. In the rack beside him were a number of the black gas bombs, each of which, dropped to earth, would release enough gas to cover a considerable area with darkness. Both Luke and Dick wore respirators filled with charcoal and sodium thio-sulphate, and beside Dick a cage containing three guinea-pigs rested.

These little rodents were so sensitive to atmospheric changes that a quantity of hydrocyanic acid too minute to affect a man would produce instantaneous death on them.

From its hiding-place off the Virginia coast the American fleet was steaming hotly southward toward Abaco Island, cruisers, destroyers, submarines. That Abaco was British territory had simply not been considered in this crisis of history.

The twelve airships that followed Dick's contained enough bombs to put the headquarters of the Invisible Empire out of business for good. The naval guns would complete the same business.

All day Dick and Luke Evans flew southwestward. At first glance, everything appeared normal. The catastrophe that had fallen upon the land was visible only in the shape of the lines of tiny figures, extending for miles, that choked all the roads radiating out of the principal cities. It was only when they were over the southern portion of Virginia that the ravages of deadly gas became apparent.

Flying low, Dick could see the fields strewn with the bodies of dead cattle. Here and there, at the doors of farmhouses, the inmates could be seen, lying together in gruesome heaps, caught and killed instantaneously as they attempted flight. Here, too, were figures on the roads. But they were figures of dead men and women.


T

hey strewed the roads for miles, lying as they had been trapped—men, women, children, horses, mules, and dogs. The spectacle was an appalling one. Dick set his jaws grimly. He was thinking that the Council had let Von Kettler escape. He was thinking of Fredegonde. But he would not let himself think of her. She deserved no more pity than the rest of the murderous crew.

Over the Carolinas the conditions were still more appalling. Here deadly gas had struck with all its concentrated power. A city materialized out of the blue distance, a factory town with all chimneys spiring upward into the blue, a section of tall buildings intersected by canyonlike streets, around it a rim of trim houses, bungalows, indicative of prosperity and comfort. And it was a city of the dead.

For everywhere around it, on all the roads, the dead lay piled on top of one another. For miles—all the inhabitants, rich and poor, business men, factory hands, negroes. There had been a mad rush as the fatal gas drove onward upon its lethal way, and all the fugitives had been overwhelmed simultaneously.

Here were golf links, with little groups strewn on the grass and fairways; here, at one of the holes, four men, their putters still in their hands, crouched in death. Here was the wreckage of a train that had collided with a string of freight cars at an untended switch, and from the shattered windows the heads and bodies of the dead protruded in serried ranks.

Dick looked back. His flight was driving on behind him. He guessed their feelings. They had sworn, as he had sworn, that none of them would return without stamping out that abomination from the earth forever.


H

e signaled to the flight to rise, and zoomed upward to twelve thousand feet. He did not want to look upon any more of those horrors. At that height, the peaceful landscape lay extended underneath, in a checker-board of farms and woodlands. One could pretend that it was all a vile dream.

He avoided Charleston, and winged out above the Atlantic, striking a straight course along the coast toward the Bahamas. The shores of Georgia vanished in the west. Dick began to breathe more freely. His mind shook off its weight of horror. Only the blue sea and the blue sky were visible The aftermath of the gale remained in the shape of a strong head breeze and white crests below.

Dick glanced at the guinea-pigs. They were busily gnawing their cabbage and carrots. The gas had evidently been entirely dissipated by the wind.

Toward sunset the low jutting fore-land of Canaveral on the east coast of Florida, came into view. Dick shifted course a little. Three hours more should see them over Abaco.

His flight had explicit instructions. As soon as the black gas had rendered visible the headquarters of the Invisible Emperor, they were to circle above, dropping their bombs. When these were exhausted, the machine guns would come into play. There was to be no attention paid to signals of surrender. They were to wipe out the headquarters, to kill every living thing that showed itself—and the navy and the marines would mop up anything left over.

The sun went down in a blaze of gold and crimson. Night fell. The moon began to climb the east. The black sea, stretching beneath, was as empty as on the day when it was created. Nothing in the shape of navigation appeared.

Two hours, three hours, and old Evans turned round in his cockpit and pointed. On the horizon a black thread was beginning to stretch against the sky. It was Abaco Island, in the Bahama group. They were nearly at their destination. An hour more—perhaps two hours, and the deadly menace that threatened America might be removed forever. Dick breathed a silent prayer for success.


T

hey were over Abaco. A long, flat island, seventy miles or so in extreme length, and fairly wide, covered with a dense growth of tropical brush and forest, with here and there open spaces, near the seacoast an occasional farm-house. Dick dropped to five thousand, to three, to one. The moon made the whole land underneath as bright as day.

There were no evidence of destruction by the hurricane. The farmhouses stood substantial and well roofed. If death had struck Abaco Island, it had been the work of man, not Nature.

Dick zoomed almost to his ceiling, until, in the brilliant moonlight, he could see Abaco Island from side to side. For the most part it was heavily wooded with mahogany and lignum vitae: toward the central portion there was open land, but there was not the least sign of any construction work.

Again he swooped, indicating to his flight to follow him. At a thousand feet he examined the open district intently. Here, if anywhere upon the island, the Invisible Emperor had his headquarters. Was it conceivable that a gas factory, hangars, ammunition depots could exist here invisibly, when he could look straight down upon the ground?

Dick's heart sank. The hideous fear came to him that Graves had been mistaken, that he had come on a wild-goose chase. This could not be the place. It was quite incredible.

Again and again he circled, studying the ground beneath. Now he could see that the tough grass and undergrowth marked curious geometrical patterns. Here, for example, was an oblong of bare earth around which the vegetation grew, and it was obviously the work of man.

Here were four squares of bare ground set side by side, with thin strips of vegetation growing between them.

Then of a sudden Dick knew! Those squares and parallelograms of bare ground indicated the foundations of buildings. He was looking down on the very site of the Invisible Emperor's stronghold!

He shouted, and pointed downward. Luke Evans looked round and nodded. He understood. He patted the camera-box with a grim smile on his old face.

CHAPTER VIII

The Magnetic Trap

U

pon those squares and oblongs of bare earth, incredible as it seemed, rose the structures of the Invisible Empire, themselves both invisible and transparent, so that one looked straight down through them and saw only the ground beneath them.

Every interior floor and girder must have been treated with the gas. They had been cunning. They must have discovered some permanent means of charging paint with the shadow-breaking gas, so that the buildings would remain invisible for months and years instead of hours.

But they had not been cunning enough. It had not occurred to them that the foundations would still be visible underneath, for the simple reason that grass does not grow without sunlight.

Dick saw old Luke Evans nodding and pointing downward. The old man picked up his end of the speaking-tube, but Dick ignored the gesture. He signaled to his flight to rise, and zoomed up, circling, and studying the land beneath.

That oblong was evidently the central building. Those four squares probably housed airplanes, and each would hold half a dozen. That elliptical building might contain a dirigible. That round patch was probably the gas factory.

Now Dick could see more patches of bare ground, extending in the direction of the sea. He gunned his ship and followed the gap among the trees to the ocean, a few miles distant. Yes, there were more evidence of activity here. Beside the water, in what looked like a deep natural harbor, was what seemed to be the foundations of a dock. Perhaps even vessels of war floated on the phosphorescent Bahama sea.


H

e circled back, his flock wheeling like a flight of birds and following him. He signaled to them to scatter. They had certainly been observed; at any moment a hail of lead might assail them invisibly out of the air. They must get to work quickly. But had they understood the significance of those bare patches?

Dick saw Luke Evans still fidgeting impatiently with his end of the speaking-tube, and picked it up.

"I'm thinking, Captain Rennell, we've got no time to lose if we want to keep the upper hand of those devils," called the old man.

"Yes, you're right," Dick answered. "Lay a trail of gas bombs all around those hangars and buildings, enough to hold them dark for some time. And keep a bomb or two in reserve."

Luke Evans shouted back. The plane was again above the structures. The old man dropped a bomb over the side, and Dick zoomed again, his flight wheeling up behind him.

Higher and higher, banking and going round in a succession of tight spirals, Dick flew. Every moment he expected the blow to fall. As he rose, Luke Evans dropped bomb after bomb. A thousand feet beneath the flight was taking up positions, hovering with the helicopters, looking up to Dick for the signal, and waiting.

Then from beneath the cloud of black gas began to rise, as Luke Evans dropped his bombs. It filled the lower spaces of the sky, blotting out the land in impenetrable darkness. That darkness, above which Dick and his flight were soaring, rose like a solid wall, built by some prehistoric race that aimed to fling a tower into the heavens.


A

nd then—the miracle! Dick gasped in sheer delight as he realized that he had made no mistake.

At first all he could see was a number of criss-crossing phosphorescent lines that appeared shimmering through the blackness underneath. They ran luminously here and there, forming no particular pattern, much like the figures on the radium dial of a watch when first they come into wavering visibility at night.

Then the lines began to intersect one another, to assume geometric patterns and curves. And bit by bit they took meaning and significance.

And suddenly the whole invisible stronghold lay revealed upon the ground beneath, a shining, dazzling play of weaving light.

Buildings and hangars stood out, clearly revealed; the rounded vault of a dirigible hangar, and the shining ribbon of a road that ran through a pitch-dark tarmac, and was evidently constructed from some gas-impregnated materials. On this tarmac was a flight of shining airplanes, ready to take off. There were the odd, ovoid figures of the aviators in their silken overalls. More figures appeared, running out from the buildings. It was clear that the sudden raid had taken them all by surprise.

Luke Evans yelled and pointed. "We've got them now, sir!" Dick heard above the whine of the helicopter engine. "We've—"

But of a sudden the old man's voice died away, though his mouth was still moving.

Dick leaned out of his cockpit and fired a single red Very light, the signal for the attack. And from each plane of his flight, beneath him, a bomb slid from its rack and went hurtling down upon the gang below, while the airplanes circled and hovered, each taking up its station.


D

ick was too late. By a whole minute he had missed his chance. He realized that immediately, for before the red light had flared from his pistol, the hostile planes were in the air. He had flown too low, and given the alarm.

It meant a fight now, instead of a mad dog destruction, and Dick did not underestimate the power of the enemy. But he felt a thrill of furious satisfaction at the prospect of battle. From every plane the bombs were falling. Underneath, ruin and destruction, and leaping flames—and yet darkness, save for the phosphorescent outlines of the buildings.

And the lines of these were broken, converging into strange criss-crosses of luminosity, as the beams fell in shapeless heaps. Dark fire, sweeping through the headquarters of the Invisible Emperor, a veritable hell for those below! A taste of the hell that they had made for others!

Then a strange phenomenon obtruded itself upon Dick's notice. Nothing was audible! The bombs were falling, but they were falling silently. No sound came up from beneath. And, except for the throbbing of his engine, Dick would have thought it had stopped. He could no longer hear it.

That terrific holocaust of death and destruction was inaudible. Skimming the upper reach of the air, high above that wall of darkness, Dick saw old Luke Evans pick up his end of the speaking-tube, and mechanically followed suit. He could see the old man's lips moving. But he heard nothing!

And now another phenomenon was borne in on his notice. His flight were perhaps five hundred feet beneath him, hovering a little above the barrage of black gas. But they were converging oddly. And there was no sight of the airplanes that Dick had just seen taking off from the invisible tarmac.


D

ick fired two Very lights as a signal to his flight to scatter. What were they doing, bunching together like a flock of sheep, when at any moment the enemy planes might come swooping in, riddling them with bullets? He thrust the stick forward—and then realized that his controls had gone dead!

He thought for a moment that a wire had snapped. But the stick responded perfectly to his hand, only it had no longer control over his plane. He kicked right rudder, and the plane remained motionless. He pushed home the soaring lever, to neutralize the helicopter and the plane still soared.

Then he noticed that the needle of his earth-inductor compass-indicator was oscillating madly, and realized that it was not his plane that was at fault.

Underneath him, his flight seemed to be milling wildly as the ships turned in every direction of the compass. But not for long. They were nosing in, until the whole flight resembled an enormous airplane engine, with twelve radial points, corresponding to their propellers, and the noses pointing symmetrically inward, like a herd of game, yarding in winter time.

And now the true significance came home to Dick. A vertical line of magnetic force, an invisible mast, had been shot upward from the ground. The airplanes were moored to it by their noses, as effectively as if they had been fastened with steel wires.

And he, too, was struggling against that magnetic force that was slowly drawing him, despite his utmost efforts, to a fixed position five hundred feet above his flight.


F

or a few moments, by feeding his engine gas to the limit, Dick thought he might have a chance of escaping. Her nose a fixed point, Dick whirled round and round in a dizzy maze, attempting to break that invisible mooring-chain. Then suddenly the engine went dead. He was trapped helplessly.

He saw old Evans gesticulating wildly in the front cockpit. The old man hoisted himself, leaned over the cowling gibbered in Dick's ear. The silent engine had ceased to throb, and the old man's shouts were simply not translated into sound.

Suddenly the flight beneath jerked downward, just as a flag jerks when it is hauled down a pole. They vanished into the dark cloud beneath. At the same time there came a jerk that dropped Dick's plane a hundred feet, and flung him violently against the rim of the cockpit.

Another followed. By drops of a hundred feet at a time, Dick was being hauled down into the darkness underneath him.

It rushed up at him. One moment he was suspended upon the rim of it, seeing the moon and stars above him; the next he had been plunged into utter blackness. Blackness more intense than anything that could be conceived—soundless blackness, that was the added horror of it. Blackness of Luke Evans's contriving, but none the less fearful on that account!

And yet, as Dick was jerked slowly downward, slowly a pale visibility began to diffuse itself underneath. The black cloud was beginning to roll away. The luminous lines began to fade, and in place of them appeared little leaping tongues of fire. In front of him Dick saw Luke Evans's form begin to pattern itself upon the darkness. He saw the form move sidewise, and caught at Luke's arm as he was about to hurl another gas bomb. "No!" he shouted—and heard no sound come from his lips.


L

uke understood. He seemed to be replacing the bomb in the rack. Beneath them now, as they were jerked downward, were fantastic swirls of black mist, and, at the bottom, a pit of fire that was slowly coming into visibility.

Dick uttered a cry of horror! Five hundred feet below his plane he saw the dim forms of his flight, still bunched together, noses almost touching. And they were dropping straight into that flaming furnace of ruin underneath, which was growing clearer every instant.

Down, jerk by jerk. Down! The black cloud was fast dispersing from the ground. The flight were hardly a thousand feet above the fire. Down—a long jerk that one! Once more! The flames leaped up hungrily about the doomed airships. Cries of mad horror broke from Dick's lips as he witnessed the destruction of ships and men.

He could see almost clearly now. The twelve ships, still retaining their nose-to-nose formation, were in the very heart of the fire. Spurts of exploding gasoline thrust their white tongues upward. There was only one consolation: for the doomed men, death must have come practically instantaneously.

From where he hung, Dick could feel the fierce heat of the flames below. In front of him, old Luke Evans sat in his cockpit like one petrified. He was feebly fumbling at his camera-box, as if he had some idea of using it, and had forgotten that it was fixed to the plane, but the old man seemed temporarily to have lost his wits.

Rushing flames surrounded the burning airships, reducing them to a solid, welded mass of incandescent metal. Dick looked down, waiting for the next jerk that would summon him to join his men. At the moment he was not conscious of either fear or horror, only intense rage against the murderers and regret that he could never bring back the news of victory.


T

he cloud had almost dissipated. In place of the phosphorescence, electric lights had appeared, making the ground beneath perfectly visible. Dick could see a number of men grouped together at the entrance to a large building, part of which had been wrecked by a bomb, though there were no evidences of fire. Other structures had been dismantled and knocked about, but what remained of them had not been charred by fire. Evidently they had been fireproofed. Perhaps the gas itself was incombustible. Only in the middle of the tarmac, where the remnants of the airplanes blazed, was there any sign of fire.

There were three machines resembling dynamos, placed one at each corner of the tarmac, equidistant from the central holocaust. A half-dozen men were grouped about each of them, and by the light from the huge reflector over each Dick saw that they were whirring busily. At the time it did not occur to him that these were the machines that were sending out the electrical force that had held the airplanes powerless.

But as he looked, his mind still a turmoil of hate and hopeless anger, he saw one of the three machines cease whirring. The group about it dispersed, the light above went out. And now his plane, as if drawn by the power of the two remaining machines, began to move jerkily again, not down toward the burning wreckage, but sidewise, away from it.

Straight out toward the side of the tarmac it moved jerked downward diagonally, until it rested only a few feet above the ground.

Then suddenly Dick felt the plane quiver, as if released from the power of the force that had held it. It nosed down and crashed, rolled over amid the wreckage of a shattered wing. The concussion shot Dick from the cockpit clear of the smashed machine.

He landed upon his head, and went out instantly.

CHAPTER IX

The Invisible Emperor

I

t was the sound of his name, spoken repeatedly, that brought Dick back to consciousness. He opened his eyes, blinking in broad daylight. He stared about him, and the first thing he saw was Luke Evans, regarding him anxiously from a little distance away. He saw that it was Luke who had spoken.

He had heard the old man distinctly. The condition of inaudibility was gone.

Not that of invisibility. Dick stared about him in bewilderment. For a moment, before he quite realized what had happened to him, he thought he had lost his mind. Underneath him was a thick rug, beneath his head a pillow; he could feel both of them, and yet all he could see was the open country, a clearing with shrubbery on either side, and, beyond that, a luxurious growth of tropical trees. Under him, to all visual appearance, was the bare ground.

He moved, and heard the clank of chains. He looked down at himself. His wrists were loosely linked to a chain that seemed to stretch tight into vacancy and end in nothing. His ankles were bound likewise.

And both chains appeared to be of solid silver, but thick enough to give them the strength of iron!

Then he perceived that old Evans was bound in the same way.

"Rennell! Rennell!" repeated the old man in a sort of whimper. "Thank God you've come out of it! I was afraid you were dead."

"What's happened?" asked Dick. "Where are we? Didn't they get us?"

"They've got us, damn them!" snarled old Evans. "All the rest burned to cinders, those fine fellows, Rennell! You were thrown unconscious, but none of my tough old bones were hurt. They pulled us out of the wreckage and brought us in here and tied us with these silver chains."

"In here? But where are we?" demanded Dick, trying to pass his hand across his aching forehead, and realizing that the chain, though it seemed fastened to nothing, was perfectly taut.


I

n one of their damned invisible houses," whimpered the old man. "They're fireproof. Nearly all our bombs fell on the tarmac, and they did hardly any damage at all. One of those devils was bragging about it to me. I couldn't see anything but his eyes. And they've taken away my gas-box," wailed old Luke.

Dick cursed comprehensively and was silent. The burning rage that filled him left him incapable of other utterance. Silver chains! They must be madmen—yes, that was the only explanation. Madmen who had escaped from somewhere, obtained possession of scientific secrets, and banded themselves together to overcome the world. If he could get the chance of a blow at them before he died!

He heard a door swing open—a door somewhere out on the prairie. Two men sprang into sudden visibility and approached him. There was nothing invisible about these men, though they had seemed to have materialized out of nothing. They wore the same black, trimly fitting uniform that Dick had seen in the White House. They were flesh and blood human beings like themselves.

"I congratulate you upon your recovery, Captain Rennell," remarked one of them with ironical politeness. "Also upon your shrewd coup. Needless to say, it had no chance of success, but we were misinformed as to the hour at which you might be expected. We thought it would take the fools at Washington a little longer to puzzle out our location—and then we did not put quite sufficient force into our hurricane. Quite an artificial one, Captain."

Dick, glaring at them, said nothing, and the one who had spoken turned to his companion, laughing, and said something in a foreign language that he did not recognize.

"His Majesty the Emperor commands your presence, and that of this old fool," said the first man. "Do not attempt to escape us. Death will be instantaneous." He drew a glass rod from his pocket, the tip of which glowed with a pale blue light.


A

gain he spoke to his companion, who moved apparently a few feet distant out on the prairie. Suddenly Dick saw old Evans' chain slacken: then Dick's slackened too. He understood that he was unbound, though his wrists and ankles were still loosely fastened.

The second man took his station beside Luke Evans and motioned to him to rise. The first man beckoned to Dick to do the same. The two prisoners got upon their feet, trailing each a length of clanking chain. Each of the two guards covered his captive with the glass rod and motioned to him to precede him.

Choking with fury, Dick obeyed. He had taken a dozen steps with his guard uttered a sharp command to halt, at the same time shouting some word of command.

The edge of a door appeared, also seeming to materialize out of space. It widened, and Dick realized that he was looking at the unpainted inner side of a door whose outside was invisible. Beyond the door appeared a flight of steps.

Dick passed through and descended them. He counted fifteen. He emerged into a timbered underground passage, well lit with lamps, filled with what seemed to be mercury vapor. Behind him walked his guard: behind the guard he heard Luke Evans shambling. Both chains were clinking, and again Dick's fury almost overcame him.

He controlled himself. He had no hope or desire for life, but he meant to strike some sort of blow before he died, if it were possible.

They turned out of the timbered passage, Dick's guard now walking at his side, the glass rod menacing his back. Dick found himself in a large subterranean room of extraordinary character. The walls were not merely timbered, but paneled. Pictures hung upon them, there were soft rugs underfoot, there was antique furniture. Everything was in plain sight.


T

here was a door at the farther end, from beyond which came the murmur of voices. Two guards in the same black uniform, but without the ornamental silver braid, stood to attention, long halberds in their hands. One spoke a challenge.

The guard at Dick's side answered. The two men stepped backward, each about two feet, and pulled the two cords on either side of a curtain behind the open door. Dick passed through.

He stopped in sheer amazement. The gorgeousness of this larger room into which he entered was almost stupefying. It seemed to have been lifted bodily from some European palace. Mirrors with gilt edges ran along the side. On the floor was a single huge rug of Oriental weave.

At the farther end was a throne of gilt, lined with red velvet in which sat a man. An old man, of perhaps eighty years, with a grey peaked beard and fierce, commanding features. On his head was a gold crown glittering with gems. About him were gathered some twoscore men and a few women.

Those ranged on either side of the throne wore, like its occupant, robes of red, lined with ermine. The rank behind wore shorter robes, less decorative, but no less extraordinary. They might all have stepped out of some medieval court.

Behind this second line, and half-encircling them, were officers in the black uniform with the silver braid.

There had been chattering, but as Dick passed through into the room it was succeeded by complete silence. Dick fixed his eyes upon the old man on the throne.

He knew him! Knew him for a once famous European ruler who had lost his throne in the war. A man always of unbalanced mentality, who, after living for years in exile, had been reported dead three years before. A madman who had vanished to make this last attempt upon the world, aided and abetted by the secret group of nobles who had surrounded him in the days of his pomp and power.


O

ld men, all of those in the first line! Madmen too, perhaps, as madness begets madness. Behind them, younger men, infected by the strange malady, and enthusiastic for their desperate cause.

Yes, Dick knew this Invisible Emperor, lurking here in his underground palace. He knew Von Kettler, too, in the second line, close to the Emperor's throne. And, among the women in their robes, grouped picturesquely about that throne, he knew Fredegonde Valmy.

Dark-haired beneath her coronet, of radiant beauty, she fixed her eyes upon Dick's. Not a muscle of her face quivered.

Then only did Dick see something else, which he had not hitherto observed, owing to its concealment by the robes of those grouped about the Emperor, and the sight of it sent such a thrill of fury through him that he stood where he was, unable to speak or move a muscle.

The throne was set on a sort of dais, with three steps in front of it. The lowest of these steps was hollow. Within this hollow appeared the head and shoulders of a man.

An elderly man clothed in parti-colored red and yellow, the time-honored garment of court fools. He was on his hands and knees, and the round of his back fitted into the hollow of the step, and had a flat board over it, so that the Emperor, in ascending his throne, would place his foot upon it.

He was kept in that position with heavy chains of what looked like gold, which passed about his neck and arms, and fitted into heavy gold staples in the wood. And the old man was President Hargreaves of the United States!


T

he President of the American Republic, chained as a footstool for the Invisible Emperor, the madman who defied the world. Dick stood petrified, staring into the mild face of the old man, still incapable of speech. Then a herald, carrying a long trumpet, to which a square banner was attached, strode forward from one side of the grotesque assemblage.

"Dog, on your knees when His Majesty deigns to admit you to the Presence!" he shouted.

The guard at Dick's side prodded him with his glass rod.

Then the storm of mad fury in Dick's heart released limbs and voice. The cry that came from his lips was like nothing human. He leaped upon the guard with a swift uppercut that sent him sprawling.

The glass rod slipped from his hands to the rug, striking the edge of his shoe, and broke to fragments. A single streak of fire shot from it, blasting a black streak across the Oriental rug.

Dick leaped toward the throne, and the assemblage, as if paralyzed by his sudden maneuver, remained watching him without moving. Then a woman screamed, and instantly the picturesque gathering had dissolved into a mob placing itself about the person of the Emperor, who sprang from his throne in agitation.

Dick was almost at the steps. But it was not at the Emperor that he leaped. He sprang to Hargreaves's side. "Mr. President, I'm an American," he babbled. "We've located this gang, we'll blow them off the face of the earth. In chains—God, in chains, sir—"

Dick stumbled over the length of his own chain that he had been dragging behind him—stumbled and fell prone upon the floor. Before he could regain his feet they were upon him.


A

 dozen men were holding him, despite his mad, frenzied struggles, and as, at length, he paused, exhausted, one of them, covering his head with a glass rod, looked up at the Emperor, who had resumed his seat.

Dick calmed himself. Still gripped, he straightened his body, and gave the mad monarch back look for look. For a moment the two men regarded each other. Then a peal of laughter broke from the Invisible Emperor's lips. And any one who heard that peal—any one save those accustomed to him—might have known that it was a madman's laughter.

He flung back his head and laughed, and the whole crowd laughed too. All those sycophants roared and chuckled—all except Fredegonde. It was not till afterward that Dick remembered that.

He stood up. "Dog of an American," he roared, "do you know why you were brought here? It was because I wanted one Yankee to live and see the irresistible powers that I exercise, so that he can go back and report on them to those fools in Washington who still think they can defy me, the messenger of the All-Highest.

"I tell you that the things I have done are nothing in comparison with the things that I have yet to do, if your insane government of pig-headed fools persists in its defiance. It is my plan to send you back to tell them that their President lies bound in gold chains as my footstool. That the hurricane which spread the gas through southern America was a mere summer zephyr in comparison with the storm that I shall send next.


A

ll the resources of Nature are at my command thanks to the illustrious chemists who have been secretly working for the past ten years to serve me. I, the All-Highest, have been commanded by the Almighty to scourge the world for its insolence in rejecting me, and especially the pig-race of Yankees whose pride has grown so great. Mine is the divinely appointed task to cast down your ridiculous democracies and re-establish the divine world-order of an Emperor and his nobility.

"That is why I have chosen, to permit so mean a thing as you to live. As for the old fool beside you, who thought to stay my power with his box of tricks—his gas-box is already being analyzed by my chemists, and in a few hours the trivial secret will be at my disposal."

"And that's just where you're wrong," piped old Luke Evans in his cracked voice. "That gas can't be analyzed, because it contains an unknown isotope, and, as for yourself, you're nothing but a daft old fool, with your tin-horn trumpery!"

For a moment the Emperor stood like a statue, staring at old Luke. The expression on his face was that of a madman, but a madman through whose brain a straggling ray of realization has dawned. It was the look upon his face that held the whole assemblage spellbound. Then suddenly came intervention.

Through a doorway in the side of the hall came one of the officers in black. He advanced to the foot of the throne and made a deep, hurried bow, speaking rapidly in some language incomprehensible to Dick.

The Emperor started, and then a peal of laughter left his lips.

"Pig of a Yankee," he shouted to Dick, "your contemptible navy's now approaching our shores, with a dirigible scout above it. You shall now see how I deal with such swine!"

CHAPTER X

The Tricks of the Trade

H

e barked a command, and instantly Dick was seized by two of the guards, one of whom—the one Dick had knocked down—took the occasion to administer a buffeting in the process of overcoming him. For the sight of the honored President of the United States—that kindly old man straining his eyes to meet Dick's own—in the parti-colored garb of red and yellow, and chained like a beast below the madman's throne, again filled Dick with a fury beyond all control.

It was only when he had been half-stunned again by the vicious blows of his captors, delivered with short truncheons of heavy wood, that at length he desisted from his futile struggle.

With swimming eyes he looked upon the gathering about the throne, which, again taking its cue from the madman, way roaring with laughter at his antics. And again Dick's eyes encountered those of Fredegonde Valmy.

The girl was not smiling. She was looking straight at him, and for a moment it seemed to Dick as if he read some message in her eyes.

Only for an instant that idea flashed through his mind. He was in no mood to receive messages. As he stood panting like a wild beast at bay, suddenly a filmy substance was thrown over his head from behind. Then, as his face emerged, and the rest of his body was swiftly enveloped, he realized what was happening.

They had thrown over him one of the invisible garments. He could feel the stuff about him, but he could no longer see his own body or limbs.

From his own ken, Dick Rennell had vanished utterly. Where his legs and feet should have been, there was only the rug, with the burn from the glass tube. He raised one arm and could not see arm or fingers.

In another moment invisible cords had been flung around him. Dick's efforts to renew the struggle were quickly cut short. Trussed helplessly, he could only stand glaring at the madman rocking with laughter upon his tinsel throne. Beside him, similarly bound, stood Luke Evans, but Dick was only conscious of the old man's presence by reason of the short, rasping, emphatic curses that broke from his lips.


T

he Emperor turned on his throne and beckoned to Von Kettler, who approached with a deferential bow.

"Nobility, we charge you with the care of these two prisoners," he addressed him. "Have the old one removed to the laboratory, and give orders that he shall assist our chemists to the best of his power in their analysis of the black gas. As for the other, take him up to the central office, and show him how we deal with Yankees and all other pigs. Show him everything, so that he may take back a correct account of our irresistible powers when we dismiss him."

"Come!" barked one of the guards in Dick's ear.

Dick attempted no further resistance. Convinced of its futility, sick and reeling from the blows he had received, he accompanied his captors quietly. There was nothing more that he could do, either for President Hargreaves or for old Luke, but he still imagined the possibility of somehow warning the approaching fleet or the occupants of the dirigible.

He was led along the passage, past the guards, and up the stairs again. The top door opened upon vacancy; it closed, and vanished. Dick felt the rugs beneath his feet, but he was to all appearances standing on a square of bare earth in the middle of a prairie.

"Come!" barked the guard again, and Dick accompanied him, trailing his silver chain. Behind came Von Kettler.

"Here are steps!" said the guard, after they had proceeded a short distance.

Dick stumbled against the lowest step of an invisible flight. The breeze was cut off, showing that they had entered a building. Underneath was a large oval of bare ground. Dick found a handrail and groped his way up around a spiral staircase, four flights of it.

"Here is a room!"


D

ick saw that widening edge of door again. The room inside was perfectly visible, though it seemed to be supported upon air. It was a spheroid, of huge size, with a number of large windows set into the walls, and it was filled with machinery. About a dozen workmen in blue blouses were moving to and fro, attending to what appeared to be a number of enormous dynamos, but there were other apparatus of whose significance Dick was ignorant. The dynamos were whirring with intense velocity, but not the slightest sound was audible.

Von Kettler stepped to a switch attached to a stanchion of white metal, surmounted by a huge opaque glass dome, and threw it over. Instantly the hum and whir of machinery became audible, the sound of footsteps, the voices of the workmen, and the creak of boards beneath their feet.

"You see, we have discovered the means of destroying sound waves as well as shadows, and it was a much simpler feat," said Von Kettler with a sneer. "Tell them that when you get back to Washington, Yankee pig. Also you might be interested to know that most of your bombs fell on camouflaged structures that we had erected with the intention of deceiving you."

He gestured to Dick to precede him, and halted him at a plain round iron pipe or rod that rose up through the floor and passed through the roof. It was surrounded by a mesh of fine wire. Attached to it were various gauges, with dials showing red and black numbers.

"This is perhaps our greatest achievement, swine," remarked Von Kettler, affably. "You shall see its operations from above." He pointed to a narrow spiral staircase rising at the far end of the room. "It is the practical application of Einstein's gravitation and electricity in field relation. It is by means of this, and the three dynamos on the ground that we were able to neutralize your engines last night and bring them down where we wanted them. You must be sure to tell the Washington hogs about that."


H

e motioned to Dick to cross the room and ascend the spiral staircase. Following him, he flung another switch similar to the first one, and instantly all sound within the room was cut off.

They ascended the winding flight and emerged upon a floor or platform. Dick felt it under his feet, but he could see nothing except the ground, far beneath him. He seemed to be suspended in the void. He stopped, groping, hesitating to advance. Von Kettler's jarring laugh grated on his ears.

"Don't be afraid, swine," he jeered. "This place is enclosed. There is a shadow-breaking device on every floor, which renders us complete masters of camouflage."

A switch snapped. Dick found himself instantly in a rotunda, roofed with glass, sections of which were raised to a height of three or four feet from the wooden base, admitting a gentle breeze. Three or four men were moving about in it, but these wore the black uniform with the silver braid, and Von Kettler's manner was deferential as he addressed them, jerking his hand contemptuously toward Dick. Grins of derision and malice appeared on all the faces.

Save one, an elderly officer, apparently of high rank, who came forward and raised his hand to the salute.

"Captain Rennell," he said, "we are at war with your nation, but we are also, I hope, gentlemen." He turned to Von Kettler. "Is it seemly," he asked, "that an officer of the American army should be brought here in chains and cords?"

"Excellency, it is His Majesty's command," responded Von Kettler, with a servile smirk that hardly concealed his elation. "Moreover, the American is to witness the forthcoming destruction of the Yankee fleet."

The elderly officer reddened, turned away without replying. Dick looked about him.


T

here was less machinery in this room. The iron pillar that he had seen came through the floor and terminated some five feet above it in another of the opaque glass domes, filled with iridescent fire. About it was a complicated arrangement of dials and gauges.

In the centre of the room was a sort of camera obscura. A large hood projected above a flat table, and an officer was half-concealed beneath it, apparently studying the table busily.

"Come, American, you shall see your navy on its way to destruction," said Von Kettler, beckoning Dick within the hood.

The officer stepped from the table, whose top was a sheet of silvered glass, leaving Von Kettler and Dick in front of it. Dick looked. At first he could see nothing but the vast stretch of sea; then he began to make out tiny dots at the table's end, terminating in minute blurs that were evidently smoke from the funnels.

"Your ships," said Von Kettler, smiling. "This is the dirigible." He pointed to another dot that came into sight and disappeared almost instantly. "They are a hundred and fifty miles away. Explain to your friends in Washington that our super-telescopic sights are based upon a refraction of light that overcomes the earth's curvature. It is simple, but it happens not to have been worked out until my Master commanded it."

Dick watched those tiny dots in fascination, mentally computing. At an average speed of fifty knots an hour, the squadron's steaming rate, they should be off the coast within three hours. The dirigible would take two, if it went ahead to scout, as was almost certain.


D

ick stepped back from beneath the hood and glanced about him. If only his arms were not bound, he might do enough damage within a few seconds to put the deadlier machinery out of commission, if only the silvered mirror. He glanced about him. Von Kettler, interpreting his thought, smiled coolly.

"You are helpless, my dear Yankee pig," he said. "But there is more to see. Oblige me by accompanying me up to the top story."

He pointed to a ladder running up beside the iron pillar through an opening in the roof, and Dick, with a shrug of the shoulders, complied. He emerged upon a small platform, apparently protruding into vacancy. Far underneath he saw the clearing, and two airplanes on the tarmac, the aviators looking like beetles from that height. He looked out to sea and saw no signs of the fleet.

"You have heard of St. Simeon Stylites, Yankee?" purred Von Kettler. "The gentleman who spent forty years of his life upon a tall pillar, in atonement for his sins? It is His Majesty's desire that you spend, not forty years, but two or three hours up here, meditating upon his grandeur, before returning to earth. It is also possible that you will witness something of considerable interest. Look out to sea!"

Dick turned his head involuntarily. He heard Von Kettler's laugh, heard the snap of a switch—then suddenly he was alone in the void.

At that snap of the switch, everything had vanished from view behind him, the building, even the platform on which he stood. His feet seemed to rest on nothing. Yet below him he could still see the airplanes, and more being wheeled out.


A

 sense of extreme physical nausea overcame him. He reeled, then managed to steady himself. He, too, was invisible to his own eyes. Involuntarily he cried out. No sound came from his lips. He stood there, invisible in an invisible, soundless void.

For what seemed an unending period he occupied himself with endeavoring to obtain the sense of balance. Then, with a great effort, he managed to loosen the cords that bound his right arm to his side. A mighty wrench, and he had slipped them up above his elbow. His right lower arm was free.

He extended it cautiously, and his hand encountered a railing. Instantly he felt more at ease. He began moving slowly around in a widening circle, and discovered that the platform was enclosed. The further side was, however, open, and he began sliding forward, foot by foot, to locate himself. Once his foot slipped over the edge, and he drew back hastily. He felt on the other side, and discovered that he was upon what seemed a plank walk, perhaps a hundred and fifty feet above the ground, with no rail on either side, and some six feet wide.

Very cautiously he shuffled his way along it. It was solid enough, although invisible, but more than once Dick walked perilously close to one edge or the other. At length he went down on his hands and knees, and proceeded, crawling, until his movements were arrested by what was unmistakably a door.

The plank bridge, then, connected the top stories of two buildings, but what the second was, there was no means of knowing. The door was barred on the other side, and did not yield an iota to Dick's cautious pressure. Dick felt the frame. Beyond was glass, reinforced with iron on the outside, the latter metal forming a sort of lattice work. Cautiously Dick began to crawl up the rounded dome.


F

oot by foot he made his way, clinging to the iron bars, until he felt that he had reached the point of the dome's maximum convexity. He wedged his feet against a bar and rested. Only now was it brought home to him that it would be impossible for him to find his way back to the plank.

A long time must have passed, for, looking out to sea, he could see the squadron now, minute points on the horizon, exuding smudges of smoke. The dirigible was still invisible. The airplanes had either left the tarmac or had been wrapped in the gas-impregnated cloth, for both they and the aviators had vanished.

Suddenly Dick had an odd sensation that the iron was growing warm.

In another moment or two he had no doubt of it. The iron bar he clutched was distinctly warm; it was growing hot. He shifted his grasp to the adjacent bar and even in that moment the heat had increased perceptibly.

Suddenly there came a vibration, a sense of movement. Dick was being swung outward. The whole dome seemed to be dropping into space. He dug his feet and fingers under the hot rods, and felt himself sliding over on his back.

Back—back, till he was lying horizontally in space, and clutching desperately at the iron bar, which was growing hotter every moment.

The sliding movement ceased. It was as if the whole upper section of the glass dome had opened outward. But the heat of the bars was becoming unbearable, and gusts of hot air seemed to be proceeding from within.

Hot or not, Dick's only alternative was to work his way back to the stable portion of the dome, or to frizzle until he dropped through space.

Clinging desperately to the bars, he began working back, reaching from bar to bar with his right hand and dragging his feet, with the clanking chain attached, from bar to bar also.


H

ow he gained the base of the dome he was never able afterward to understand. The heat had grown intolerable; his hands were blistering. Somehow he reached it. He rested a moment despite the heat. But to find the plank walk was clearly impossible. In another minute he must drop. Better that than to fry there like St. Lawrence on his griddle.

And then, just when he had resigned himself to that last drop, there came an unexpected diversion. Almost beside him a window was hung back. A man looked out. Dick saw one of the workmen in the blue blouses, and, behind him, within the dome, what seemed like an empty room.

Dick was slightly above the man. As his head and shoulders appeared, he let himself go, landing squarely across his back. He slid down his shoulders through the open window into the interior of the dome.

The man, flung against the frame of the window by the shock, uttered a piercing cry. Before he could recover his stand, or take in what had happened to him, Dick had gained his feet and leaped upon him. His right hand closed upon his throat. He bore him to the floor and choked him into insensibility.

CHAPTER XI

In the Laboratory

N

ot until the man's struggles had ceased, and he lay unconscious, panting, and blue in the face, did Dick release him. Then he looked about him.

Save for the workman, he was alone in a rotunda, open to the sky, and, as he had supposed, the whole upper portion of the dome had been flung back, leaving an immense aperture into which the sun was shining, flecking the interior with shafts of light. The temperature, despite the opening of the dome, must have been in excess of a hundred and twenty-five degrees.

There was nothing except an immense central shaft, up which ran a hollow pole of glass, cut off by the invisible paint at the summit of the dome. The inside of this glass pole was glowing with colored fires, and it was from this that the intolerable heat came, though its function Dick could not imagine.

One thing was clear: It was growing hotter each moment. To remain in that rotunda meant death within a brief period of time.

And there was no way out! Dick glared around him, searching the glass walls in vain. No semblance of a stairway or ladder, even. Yet the workman must have entered by some ingress—if only Dick could discover it!

He began running round the interior of the dome in the brilliant sunshine, searching frantically for that ingress. And it was growing hotter! The sweat was pouring down his face beneath the invisible garment.

Dick was vaguely aware that the silence switch had been thrown in the room, for his feet made no sound, but the knowledge was latent in his mind. Two or three times he circumnavigated the interior of the dome, like a rat in a trap.

Then suddenly he saw a section of the flooring rise in a corner, and a workman in a blue blouse appear out of the trap door.


H

e stood there, his face muscles working as he shouted for his companion, but no sound came from his lips. He looked about him, and saw the unconscious man beside the window. He started in his direction.

With a shout, Dick hurled himself toward him. And he checked himself even as he was about to leap. For he realized that the second workman neither saw nor heard him.

Yet some subconscious impression of danger must have reached his mind, for the workman stopped too, instinctively assuming an attitude of defense. Dick gathered a dozen links of his wrist-chain in his right hand, leaped and struck.

The workman crumpled to the floor, a little thread of blood creeping from his right temple.

It was the thing upon which Dick looked back afterward with less satisfaction than any other, leaving the two unconscious men in that room of death. Yet there was nothing else he could have done. He ran to the trap, and saw a ladder leading down. In a moment he had swung himself through and closed the trap behind him.

The material that lined the walls below must have had almost perfect insulating qualities, for the temperature here was no hotter than in the Bahamas on a hot summer day. Dick scrambled down the ladder and found himself in a machine-shop. Nobody was there, and tools of all sorts were lying about, as well as machinery whose purpose he did not understand. A pair of heavy pliers and a vise were sufficient to rid Dick of his wrist and ankle chains in a minute or two. With a knife he slashed the cords of invisible stuff that bound him. He stood up, cramped, but free.

He picked up an iron bar that was lying loose on a table beside a machine, and advanced to the staircase in one corner of the shop. As he approached it, another workman came running up.


D

ick stood aside in an embrasure in the wall partly occupied by a machine. The man passed within two feet of him and never saw him. Only then did Dick quite realize that he was actually invisible.

The moment the man had passed him, Dick ran to the staircase. He descended one flight; he was half way down another when a yell of pain and imprecation came to his ears. He knew that voice: it was Luke Evans's!

With three bounds Dick reached the bottom of the stairs. He saw a large room in front of him. No mistaking the nature of this room; it was an ordinary laboratory, fitted out with the greatest elaboration, and divided into two parts by paneling. And sight and sound were on.

In the part nearer Dick three men were grouped about a large dynamo, which was sending out a high, musical note as it spun. Levers and dials were all about it, and above it was the base of the glass tube that Dick had seen above. In the other part were five or six men. Three of them were testing some substance at a table; three more were gathered about old Luke Evans, whose silver chains had been removed and replaced by ropes, which bound his limbs, and also bound him to a heavy chair, which seemed to be affixed to the ground. One of the three had a piece of metal in a pair of long-handled pliers. It was white hot, and a white electric spark that shot to and fro between two terminals close by, showed where it had been heated.

Dick started; he recognized one of the three men as Von Kettler. He moved slowly forward, very softly, his feet making no sound on the fiber matting that covered the floor.


D

id that feel good, American swine?" asked Von Kettler softly, and Dick saw, with horror, a red weal on the old man's forehead. "Now you are perhaps in a more gracious mood, Professor? The unknown isotope in that black gas of yours—you are disposed to give us the chemical formula?"

"I'll see you in hell first," raved old Luke Evans, writhing in his chair.

Von Kettler turned to the man holding the white-hot metal, and nodded. But at that moment a door behind Evans's chair opened, and Fredegonde Valmy appeared in the entrance. Von Kettler turned hastily, snatched the pliers from the man's hand, and laid the metal in a receptacle.

But the girl had seen the action. She looked at the weal on Luke's forehead, and clenched her hands; her eyes dilated with horror.

"You have been torturing him, Hugo!" she cried.

"Freda, what are you doing in here? Oblige me by withdrawing immediately!" cried Von Kettler.

"Where is Captain Rennell?" the girl retorted. "I will know!"

"He is upstairs, watching the approaching Yankee fleet, and waiting to see its destruction," returned the other.

"You are lying to me! He has been killed, and this old man has been tortured!" cried Fredegonde. "I tell you, Hugo Von Kettler, you are no longer a half-brother of mine! I am through with you!"

"Unfortunately," sneered Von Kettler, "it is not possible to dispose of a family relationship so easily."


I

t is cheap to sneer," the girl retorted. "But you sang a very different song when you were in the penitentiary, in terror of death, and you begged me to come and throw you the invisible robe through the bars. You promised me then that you would abandon this mad enterprise and come away with me. You swore it!"

"I have sworn allegiance to my Emperor, and that comes first," retorted Von Kettler. "Oblige me by retiring."

"I shall do nothing of the sort," cried the girl hysterically. "When you used me as a tool in your enterprises in Washington, you played upon my patriotism for my conquered country. I thought I was undertaking a heroic act. I didn't dream of the villainy, the cold-blooded murder that was to be wrought.

"You've kept me here virtually a prisoner," she went on, with rising violence, "an attendant upon that old madman, your Emperor, and his sham court, while more murder is being planned. Where is Captain Rennell, I say?" She stamped her foot. "I demand that he and this old man be set at liberty at once. Hugo," she pleaded, "come away with me. Don't you see what the end must be? This is no heroic enterprise, it is wholesale murder that will arouse the conscience of civilized mankind against you! Order that the vortex-ray be turned off," she went on, looking through the opening in the partition toward the dynamo. "That gas—you cannot be so vile as to send it forth again, to destroy the American ships?"

"My dear Freda," retorted the young man coolly, "the vortex-ray is already charged with the gas, and at a height of twenty thousand feet it is now creating a vacuum that will send the gas upon the wings of a hurricane straight up the Atlantic seaboard. It will obliterate every living thing on board the battleships, from men to rats, and this time we mean to reach New York.

"As for that swine Rennell," he went on, "you heard His Majesty announce his intention of sending him back to Washington with the information of our irresistible power. Of course I know you are in love with him, and that these qualms of conscience are due to that circumstance."


B

ut Dick hardly heard the latter part of Von Kettler's remarks. Suddenly the significance of the dynamo and the superheated room above had come home to him. He had read of such a project years before, in some newspaper, and had forgotten about it until that moment.

By sending a high-tension current almost to the limits of the earth's atmosphere, the article had said, a vortex or vacuum could be set up which would create a hurricane.

The tremendous pressure of the in-rushing air would make a veritable cyclone, which, taking the course of the prevailing winds, would rush forth on a mission of widespread disaster.

And on this hurricane would go the deadly gas, infinitely diluted, and yet deadly to all life in its infinitesimal proportion to the atmosphere.

And the American fleet was now approaching the Bahama shores.

Dick forgot Luke Evans, everything else, as the significance of that mechanism in the next room came home to him. He ran like a madman through the space in the partition, and, raising the bar aloft, brought it thudding down upon the dials, twisting and warping them.

He struck at the hollow pole, but, glass or not, it defied all his efforts. He seized a heavy lever and flung it into reverse—and two others.

Yelling, the three attendants broke and ran. Out of the laboratory the six came running, collided with the three. Behind them Dick could see Fredegonde Valmy, a knife in her hand, slashing at Luke Evans's bonds.

Dick swung his bar and brought it crashing down on a head, felling the man like a log. He saw Von Kettler pull one of the glass rods from his pocket and fire blindly. The discharge struck a second attendant, and the man dropped screeching, his clothes ablaze.

Somebody yelled, "He's there! Look at his eyes!" and pointed at Dick's face.


D

ick leaped aside and swung the rod again, felling a third man. The others turned and ran. Von Kettler in the van, broke through the door behind Luke Evans's chair, and disappeared.

Dick ran back to where the old man was standing beside the girl, the discarded ropes at his feet. He flung his hood back. "Luke, don't you know me?" he shouted.

It was creditable to Luke Evans's composure that, though Dick must have presented the aspect of nothing more than a face floating in the air, he retained his composure.

"Sure I know you, Rennell," replied the old man. "And you and me's going to best them devils yet."

"But the fleet—it's approaching Abaco," Dick cried. "I've got to warn them."

Fredegonde seized him by the arm.

"Come with me," she cried. "If they find you here, they'll kill you."

Dick hesitated only a moment, then followed the girl as she dashed for another door on the same side of the laboratory as that by which Von Kettler and his men had fled. They dashed down the staircase, and a corridor disclosed itself at the bottom. The girl stopped.

"There is a private way—the Emperor's," she panted. "He had it constructed—in case of necessity. I got the keys. I was planning—something desperate—to stop these murders; I didn't know what."

Dick seized her by the arm. "What keys?" he demanded. "The key to the place where President Hargreaves is?"

"Yes, but—"

"We must get him. Where is he?"

"In a cell beneath the throne room. That's overhead. But they'll catch us—"

"Which is the key?" asked Dick.

The girl produced three or four keys, fumbled with them, handed one to Dick. "This way!" she cried.


T

hey ran along the corridor. Two guards appeared, moving toward them under the electric lights. At the sight of the girl running, and Luke Evans, they stopped in surprise.

Dick had pulled the hood back over his head. He ran toward them, wielding the iron bar. A mighty swing sent the two toppling over, one unconscious, the other bruised and yelling loudly.

"Here! Here!" gasped Fredegonde, stopping before a door.

Dick fitted the key to the lock and turned it. Inside, upon a quite visible bed, sat President Hargreaves, unchained. He looked up inquiringly as the three entered.

"Mr. President," said Dick, throwing back his hood, "I'm an American officer, and I want to save you. There's not much chance, but, if you'll come with me—"

Hargreaves got up and smiled. "I'm not a military man, sir," he answered, "but I'm ready to take that chance rather than—"

He did not complete the sentence. Shouts echoed along the corridor behind them. Dick replaced his hood, handed the keys back to the girl. "Take Mr. Hargreaves to any place of temporary safety you can," he said. "And Mr. Evans. I'll hold them!"

"It's right here. This door!" panted the girl, indicating a door at the end of the passage.

The three ran toward it. Dick turned. Five or six guards with Von Kettler at their head, were running toward him. They saw the three fugitives and set up a shout.

Dick had a quick inspiration. He dashed back into the cell, seized the light bed, and dragged it through the doorway into the passage, just in time to send Von Kettler and two others sprawling. He brought down the bar upon the head of one of them, shouting as he did so.

Then he became aware that the passage was flooded with sunshine. Fredegonde had got the door open.

He darted back, passed through in the wake of the three, and slammed it shut. Fredegonde turned the key. Instantly Dick found himself with his three companions upon the prairie. Not a vestige of the buildings was apparent anywhere, except for the patches of brown earth.

CHAPTER XII

Von Kettler's End

F

redegonde took command, repressing her agitation with a visible effort. "They cannot break down that door," she said, "and they dare not ask for another key. It will take them a minute or two to go back and reach us around the building. But there may be a score of people watching us. Let us walk quietly toward the thickets. If I am present, they will not suspect anything is wrong."

But Dick stood still, driven into absolute immobility by the conflicting claims of duty. For overhead, high in the blue, was an American dirigible.

And at his side was the President of the United States. One or other of them he must sacrifice.

He chose. He ran forward without answering. Those squares of brown earth, set side by side, were the airplane hangars, and he meant to seize an airplane, if he could find one beneath its coat of invisibility, and fly to warn the dirigible and the fleet.

A curious wind was blowing. It seemed to come swirling downward, as no wind that Dick had ever known. It was growing in violence each moment, beating upon his face.

As he ran, he was aware of Luke beside him. He heard shouting all about them. Luke had been seen. Not only Luke, but Hargreaves, who was running after Luke, with Fredegonde trying in vain to change his intentions. At the edge of the first brown patch Dick collided violently with the wall of the invisible hangar, and went reeling back. The shouts were growing louder.

"Wait!" gasped Luke Evans. He had something like a large watch in his hand. He held it out like a pistol, and from it projected a beam of the black gas.

Then Dick remembered Colonel Stopford's words: "He showed me a watch and said the salvation of the world was inside the case. I thought him insane."


I

nsane or not, old Luke Evans had concealed the tiny model of the camera-box to good purpose. As he swept the black beam around him, the whole mass of buildings sprang into luminosity, the figures of a score of men, grouped together, and advancing in a threatening mass, some distance away—and more.

Two airplanes, standing side by side upon the tarmac, just in front of the hangar—not mere pursuit planes, but six-seaters, formidably armed, with central turrets and bow and rear guns, and propellers revolving.

Two mechanics stood staring in the direction of the little group.

"I'm with you," gasped Hargreaves. "I'm not a military man, but I've got fighting blood, and I come of a fighting race."

Dick leaped and once more swung the iron bar. The nearer of the two mechanics went down like lead, the second, seeing his companion bludgeoned out of the air, turned and ran.

Dick shouted, pointing. Fredegonde jumped into the plane, and the President scrambled in behind her. The group, dismayed by the black beam, which Luke Evans was now turning steadily upon them, had halted irresolutely. But suddenly a head appeared, moving swiftly through the air toward the plane. It was Von Kettler, with hood flung back, the face distorted with rage and fury.

At his yells, the whole crowd started forward. Dick leaped into the central cockpit, swung the helicopter lever. Something spitted past his face, and a long streak appeared on the turret, where the gas-paint had been scored. But he was rising, rising into that increasing wind....


H

e heard a yell of triumph behind him. And that yell of Von Kettler's was his undoing. There is the telepathy between close friends, but there is also telepathic sympathy between enemies, and in an instant Dick understood what that shout of triumph portended.

He was rising into the line of magnetic force that would anchor his airplane helplessly, and leave it to be jerked down and held at Von Kettler's mercy.

He released the helicopter lever and opened throttle wide. For an instant the heavy plane hung dangerously at its low elevation, threatening to nose over. Then Dick regained control, and was winging away toward the sea, while yells of baffled fury from behind indicated the chagrin of his enemies.

He glanced up. Thank heaven the dirigible had not approached the trap. It was apparently circling overhead. Of course the observers had seen nothing, had no conception that the headquarters of the Invisible Empire lay below.

And yet it seemed to be drifting aimlessly back toward the fleet—erratically, as if not under complete control. And Dick could see the ships about a mile offshore, apparently drifting too. They were moving as no American squadron ever moved since the day the first hull was launched, for some of them, turned bow inward toward others, seemed upon the point of collision, while others were lagging on the edge of the formation, as if pointing for home.

Then suddenly the awful truth dawned upon Dick. The occupants of ships and dirigible alike had been overcome by the deadly gas.


D

ick banked, turned, leaned forward and shouted to Luke Evans, and, when the old man turned his head, indicated to him to sweep the tarmac with his ray.

The thread of black, broadening into a truncated cone, revealed nothing save the luminous outlines of the buildings. Apparently the tarmac was deserted. It was queer, too, that the silence of the night before was gone. Dick shouted again, to assure himself of what he knew already, and heard his own voice again.

Something had happened, something unexpected——or perhaps the crew of the Invisible Emperor, satisfied with the effects of the deadly gas, had not thought it necessary to go to any further trouble.

Suddenly Dick discovered that he was almost within the circle of the line of magnetic force. Hurriedly he threw over the stick and kicked rudder. It was not till he was again approaching the seashore that it occurred to him that the force, too, was not in operation.

He opened throttle wide and shot seaward. He must ascertain what had happened, and, if not too late, give warning without delay.

Then suddenly the vicious rattle of gunfire sounded in Dick's ears, and, materializing out of the sky, came Von Kettler's face. Startled for an instant, Dick quickly realized that it was Von Kettler in his plane, with his hood thrown back.

And Dick realized that his own hood was thrown back. Two faces and nothing else, were the whole visible setting for battle.

But that look upon Von Kettler's face was even more demoniacal than before. Mad with rage at the prospective escape of his prey, and infuriated by his half-sister's appearance in the plane, Von Kettler had thrown all caution to the winds. In his insane hatred he was prepared to shoot down Dick's plane and send Fredegonde to destruction with it.


I

f Dick chose to replace his hood he would have the madman at his mercy. And, if he had thought about it, he would have done so, with Fredegonde sitting behind him. But the idea did not enter his mind. Consumed with rage almost equal to Von Kettler's, he only saw there the face of one of those who had inflicted an unspeakable outrage upon the President of his country.

The memory of old Hargreaves, chained before the mock-Emperor's throne, enraged Dick more than the holocaust of lives taken by the assassins.

He shouted a wild answer to Von Kettler's challenge as his plane sped by, and banked. At that moment there came a roaring concussion that shook the plane from prop to tail.

Dick turned his head. Somehow, President Hargreaves had contrived to get the rear gun into action, and now he was staring at it as if he could not believe that he had fired it.

And that action heartened Dick wonderfully. As Von Kettler's face appeared again, he loosed his turret gun in a sweeping blast, and heard Von Kettler's gun roar futilely.

Again they crossed each other's path, and again and again, two faces, only able to gauge roughly the position of their planes. Neither man had succeeded in injuring the other.

Once old Lake turned his black ray upon Von Kettler, and for, a moment the plane stood out luminously in the blackness, but Dick leaned forward and yelled to the old man to desist.

And once Dick looked back and saw Fredegonde crouched in her cockpit with eyes wide with terror. And yet he read in her eyes the same determination she had expressed in the laboratory. She was through with her half-brother.


A

ll this while the wind had been increasing, making it difficult to maneuver the heavy plane; but now, of a sudden there came a dead lull, and then, with a whining sound, the wind rushed in again.

But this was a wind still more unlike any that Dick had ever known. A mighty gale that revolved circularly, but downward too, like a vortex, catching the plane and sweeping it into an ever tightening circle.

A man-made gale, upon whose wings the poison gas would spread northward again, carrying unlimited destruction with it. Dick fought in vain to free himself.

He was revolving as in a whirlpool, and it required the utmost presence of mind and watchfulness to hold the plane steady. Round and round he spun—and then, suddenly, out of the void materialized Von Kettler's face.

Von Kettler, helpless too, was spinning round upon the opposite side of the vortex. Thus each airship was upon the tail of the other, and it was a matter of chance which would get the other within the ringsights of the turret gun.

Von Kettler was so near that his shouts of fury came fitfully to Dick's ears as the wind carried them. Dick, working the controls, knew that not for an instant could he direct his attention from them in order to fire his gun, and the moment Von Kettler attempted to do so, he was doomed.

Round and round, struggling, battling in vain—and once more the concussion of the rear gun shook the plane. And a shout from the President reached Dick's ears.

Dick turned his head for an instant, long enough to see Von Kettler spinning down through the vortex. And he was going down afire. President Hargreaves, "no military man," had got him, the second time he had ever aligned a gun-barrel upon a target.

"Bravo, sir, bravo!" Dick shouted.

And desperately he flung the stick forward and nosed down.


N

o gale, man-made or heaven-made, could carry on its wings three-quarters of a ton of armored, turreted airship. Swirling like a leaf, the plane broke through the clutch of the blast. Instantly it grew calm. Outside that vortex, hardly a breath of air was stirring. It was as if the whole fury of the air was concentrated within that circle.

The ground came rushing up. Once more Dick tried to head seaward. With flying speed lost, he was calculating the exact moment in his downward rush when he could hope to resume control. Would that moment come before he crashed?

At less than a hundred feet he partly regained control. For a moment the plane seemed to fly on an even keel. Then her nose went down as her speed slackened. And this time there was no salvation.

Working desperately to save her, Dick saw the ground loom up before him. He heard the crash as the plane broke into splintering ruin ... he had a last vision of old Luke clutching his precious watch: then everything was dissolved in darkness....

CHAPTER XIII

You Can't Down the Marines

H

e's pulling out of it! Keep it up, Gotch!"

Dick heard the words and opened his eyes. He stared in amazement at the faces about him. Honest American faces under tropical helmets and above a uniform that he had never expected to see again. It couldn't be real. And yet it was. One word broke from his lips:

"Marines!"

"He's got it. Don't let him slip, Gotch.", grinned one of the friendly faces, and the man named Gotch, who presumably had some qualifications for his job, continued what was meant to be a gentle massage of the nerve centers along Dick's spine.

"I'm all right." Dick muttered, beginning to realize his surroundings. He was lying on a strip of prairie near the beach, on which the waves were breaking in low ripples about a motorboat that was drawn up.

He sat up. The world was swimming about him, but he seemed to have no broken bones. Not far away was the wrecked plane, an incongruous mass of streaks where the fabric had ripped through the gas-paint. "Where are the others?" Dick muttered.

Then he was aware of Fredegonde Valmy lying with a white face under a shrub. Her eyes were open, and turned toward him.

He heard Luke Evans's voice. The old man hobbled round from Dick's back, one arm in a bandage.

"She's hurt rather bad, Rennell, but we won't know how bad till we can get her away," he said. "You've been lying here about an hour, since we crashed. President Hargreaves made them take him to the fleet in the other motorboat to see what he could do. He's assumed command.

"You see, Rennell, that damn gas caught the fleet and put pretty near every man out of commission for good. But these fellows wasn't going to give up. So, since all their officers were gone, they took two of the boats and their arms and equipment, and came ashore to settle accounts. And they won't believe there's anybody on the island or any buildings. And I can't make 'em believe it. God, Rennell, those invisible devils may attack us at any moment. I don't understand what they're waiting for."

Gotch spoke: "We know you're Captain Rennell, sir. And this gentleman, we know him too, but he seems a bit queer in his head. Talking of the Invisible Emperor's headquarters on this island, a mile or so inland. The only invisible thing we've found is that piece of a garment we pulled off you."

"I broke my watch ray machine in the fall, and I can't make them believe, Rennell," almost wept old Evans. "Tell them I'm not crazy."

Dick got upon his feet with an effort, staggered a little, then made his way to Fredegonde. He kneeled down beside the girl. She was conscious, and smiled faintly, but she could not speak. He pressed her hand, rose, and came back. "Mr. Evans is not crazy," he said. "The headquarters of the gang is over there." He pointed. "Didn't President Hargreaves tell you?"

"He was kind of incoherent, sir." The marines looked at one another, wondering. Was Captain Rennell crazy too?

"We've had scouts out through the jungle, sir. There's nothing within five miles of here. They had a clear view through to the sea from the top of a hill."

"I've been there." Dick spoke with conviction. "I must tell you they've got devices that make them practically irresistible. That gas and other things. And they're invisible. But if you boys are willing to follow me, I'll lead you. It means death. I don't know what they're waiting for. But—are you willing to follow me?"

"We'll follow you, sir"—after a pause, during which Dick read in their eyes the desire to humor a crazy man. "We'll follow to hell, sir—if that gang's really there."

"Take your arms, then!" Dick pointed to the stacked rifles.

A minute later the twenty-odd Marines, forming an open line that extended from one side of the clearing to the other, were on their way toward the headquarters of the gang. And Dick, leading them, though his head was reeling, felt as if his own reason was slipping from him. Had he only dreamed all this? Was it possible that the headquarters of the Invisible Emperor existed on this desolate prairie? If it was true, why had they suddenly become silent, inert? Why had they not long ago wiped out these few Marines? And the gale—was it now sweeping northward on its mission of destruction?


H

alf an hour passed. Then the brown patches of the foundations came into view upon the open ground. Here were the hangers, here was the central building with the Emperor's headquarters. And nothing was visible, nothing stirred, yet at any moment Dick expected the rattle of machine-gun bullets or some more terrific method of destruction.

"Halt!" The line stood still. "I am going forward ahead or you. You'll follow at a distance of twenty paces. When you see me stop, feel for the door in the wall, and if I disappear, follow me. You understand?"

The Marines assented cheerfully. No harm in humoring this poor devil of an officer who had crashed and lost his wits. Like Luke Evans, shambling up through the line to Dick's side. Dick advanced. At any moment now the concentrated fire of the Emperor's men should blast them all to smithereens. Nothing happened.

And it was no dream, for Dick's outstretched hand encountered the exterior wall of the building. He had gauged his way accurately, too, for a step or two brought him to the door. He stepped inside. He was inside the private door that led to the Emperor's quarters, through which he had passed with Fredegonde, Hargreaves, and Luke Evans in their flight. It had been broken down, contrary to the girl's predictions, and the deserted passage within was perfectly visible to them all.

Stupefied, the Marines bumped and jostled with each other as they crowded in. If they had been anything but Marines, their own heads might have been turned at the discovery of this sudden materialization of a building out of nothingness.

Being Marines, they only grinned sheepishly, and followed along the corridor.


T

he first human being they saw was one of the guards, in a black tunic. He was leaning against a wall, and he was a human being no longer. He looked as if he was asleep, but he was stone dead, with a placid look on his face.

Two more dead guards lay across each other, with smiles on their faces: and there was a workman in a blue blouse who had been in a tremendous hurry to get somewhere, from his appearance, and had never got there. He had fallen asleep instead, and never wakened.

Dick found a stairway and led the way up. He thought it ran up to the laboratory, but, instead, the room into which he emerged was the ante-room of the Invisible Emperor's audience hall. Six dead guards lay in a heap in front of the curtain, and they had died as unconcerned as their fellows, to judge by the pacific expressions on their faces.

Dick passed through into the throne room. The Marines, behind him, for the first time uttered exclamations of awe—of pity.

The terrific scene that met Dick's eyes would be burned into his brain till his last day.

Upon his throne, head flung back, sat the Invisible Emperor, his features set in a sardonic leer of death. And all about him, some sitting, some lying, supporting one another, were his court, officers in black uniforms with the silver braid, and women in court dress. And all were dead too. But they had not known they had died. They had fallen asleep—upon the instant that their own volatile gas reached them.


I

 guess that's the explanation, sir," said old Luke Evans. "Those devils made the whirlwind and charged it with the gas. But when you reversed that lever, you reversed the process. Instead of projecting the force outwardly, you made a suction, and every atom of the gas that hadn't travelled beyond the radius came rushing back and filled the building. If we'd entered a half-hour later, we'd have been dead ones ourselves, but the gas was volatile enough to disperse through the chinks and crannies. Anyway, it's all over now."

Yes, it was all over, Dick thought, as he sat in his deck chair upon the cruiser that was bearing him northward. The menace to world government had been destroyed and with it all who had been behind it. There would be a new order in the world, a new and kindlier government. Men would feel closer to one another than in the past. Half the personnel of the fleet had escaped the invisible death, and only one cruiser and the dirigible had been lost in the confusion. There would be a great reception when they put into Charleston.

Dick bent over Fredegonde, who was asleep in her chair beside him. The ship's surgeon had promised recovery for her. She shouldn't suffer for her half-voluntary part in the business, Dick said to himself. It was going to be his task to help her to forget.