Grant Pemberton sat up suddenly in his berth, every sense straining and alert. What was it that had awakened him in the deathly stillness of the space-flier? His right hand slid under the pillow and clutched the handle of his gun. Its firm coolness was a comforting reality.

There it was again. A tiny scratching on the door as though someone was fumbling for the slide-switch. Very quietly he sat, waiting, his finger poised against the trigger. Suddenly the scratching ceased, and the panel moved slowly open. A thin oblong patch glimmered in the light of the corridor beyond. Grant tensed grimly.

A hand moved slowly around the slit--a hand that held a pencil-ray. Even in the dim illumination, Grant noted the queer spatulate fingers. A Ganymedan! In the entire solar system only they had those strange appendages.

Pemberton catapulted out of his berth like a flash. Not a moment too soon, either. A pale blue beam slithered across the blackness, impinged upon the pillow where his head had lain only a moment before. The air-cushion disintegrated into smoldering dust. Grant’s weapon spat viciously. A hail of tiny bullets rattled against the panel, and exploded, each in a puffball of flame.

But it was too late. Already the unknown enemy was running swiftly down the corridor, the sucking patter of his feet giving more evidence of his Ganymedan origin. Pemberton sprang to the door, thrust it open just in time to see a dark shape disappearing around a bend in the corridor. There was no use of pursuit; the passageway ended in a spray of smaller corridors, from which ambush would be absurdly easy.

HE glanced swiftly around. The corridor was empty, silent in the dim, diffused light. The motley passengers were all sound asleep; no one had been disturbed by the fracas. Earthmen, green-faced Martians, fish-scaled Venusians, spatulate Ganymedans and homeward-bound Callistans, all reposing through the sleep-period in anticipation of an early landing in Callisto.

All were asleep, that is, but one. That brought Pemberton back to the problem of his mysterious assailant. Why had this Ganymedan tried to whiff him out of existence? Grant frowned. No one on board knew of his mission, not even the captain. On the passenger list he was merely Dirk Halliday, an inconspicuous commercial traveler for Interspace Products. Yet someone had manifestly penetrated his disguise and was eager to remove him from the path of whatever deviltry was up. Who?

Grant gave a little start, then swore softly. Of course! Why hadn’t he thought of it before! The scene came back to him, complete in every detail, as though he were once more back on Earth, in the small, simply furnished office of the Interplanetary Secret Service.

The Chief of the Service was glancing up at him keenly. Beside him was a tall, powerfully shouldered Ganymedan, Miro, Inspector for Ganymede. Grant looked at him with a faint distaste as he sat there, drumming on the arm of his chair with his spatulate fingers, his soft-suction padded hoofs curled queerly under the seat. There was something furtive, too, about the red lidless eyes that shifted with quick unwinking movements.

But then, Pemberton had small use for the entire tribe of Ganymedans. Damned pirates, that’s all they were. It was not many years back since they had been the scourge of the solar system, harrying spatial commerce with their swift piratical fliers, burning and slaying for the mere lust of it.

That is, until an armada of Earth space-fliers had broken their power in one great battle. The stricken corsairs were compelled to disgorge their accumulations of plunder, give up all their fliers and armament, and above all, the import of metals was forbidden them. For, strangely enough, none of the metallic elements was to be found on Ganymede. All their weapons, all their ships, were forged of metals from the other planets.

It was now five years since Ganymede had been admitted once again to the Planetary League, after suitable declarations of repentance. But the prohibitions still held. And Grant placed small faith in the sincerity of the repentance.

The Chief was speaking.

“We’ve called you in--Miro and I,” he said, in his usual swift, staccato manner, “because we’ve agreed that you are the best man in the Service to handle the mission we have in mind.”

Grant said nothing.

“It’s a particularly dangerous affair,” the Chief continued. “Five great space-fliers, traveling along regular traffic routes, have all vanished within the space of a month--passengers, crews and all. Not a trace of them can be found.”

“No radio reports, sir?”

“That’s the most curious part of the whole business. Everyone of the fliers was equipped with apparatus that could have raised the entire solar system with a call for help, and yet not the tiniest whisper was heard.”

The Chief got up and paced the floor agitatedly. It was plain that this business was worrying him. Miro continued to sit calmly, seemingly indifferent. “It’s uncanny, I tell you. Gone as though empty space had swallowed them up.”

“You’ve applied routine methods, of course,” Grant ventured.

“Of course,” the Chief waved it aside impatiently. “But we can’t discover a thing. Battle fliers have patrolled the area without success. The last ship was literally snatched away right under the nose of a convoy. One minute it was in radio communication, and the next--whiff--it was gone.”

“Where is this area you mention?” Already Pemberton’s razor-edged brain was at work on the problem.

“Within a radius of five million miles from Jupiter. We’ve naturally considered placing an embargo upon that territory, but that would mean cutting off all of the satellites from the rest of the system.”

Miro stirred. His smooth slurred voice rolled out.

“And my planet would suffer, my friend. Alas, it has already suffered too much.” He evoked a sigh from somewhere in the depths of his barrel chest, and tried to cast up his small red eyes.

Grant suffered too, a faint disgust. Damn his eyes, what business had an erstwhile pirate, not too recently reformed, being self-righteous?

“Miro thinks,” the Chief continued unheeding, “that the Callistans know more about this than they admit. He has a theory that Callisto is somehow gathering up these ships to use in a surprise attack against his own planet, Ganymede. He says Callisto has always hated them.”

“Damn good reason,” Grant said laconically.

Miro’s lidless eyes flamed into sudden life. “And what do you mean by that, my friend?”

Pemberton replied calmly. “Simply that your people have harried and ravaged them for untold centuries. They were your nearest prey, you know.”

Miro sprang to his feet, his soft suction pads gripping the floor as though preparatory to a spring. Gone was the sanctimonious unction of his former behavior; the ruthless savage glared out of the red eyes, the flattened fingers were twisting and curling.

“You beastly Earthling,” he cried in a voice choked with rage, “I’ll--”

The Chief intervened swiftly. “Here, none of that,” he said sharply to Miro. “Don’t say anything you’ll regret later.” Then he turned to Grant, who was steadily holding his ground: “There was no reason, Pemberton, to insult an inspector of the Service. Consider yourself reprimanded.” But the edge of the rebuke was taken off by the slight twinkle in the Chief’s eye.

Somehow a truce was patched up. Grant was to ship as an ordinary passenger on the Althea, the great passenger liner that plied between Callisto and the Earth. It was not his duty to prevent the disappearance of the vessel, the Chief insisted, but to endeavor to discover the cause. It was up to Grant then to escape, if he could, and to report to Miro on Ganymede immediately with his findings. Miro was leaving by his private Service flier at once for Ganymede, to await him. Grant thought he saw a faint sardonic gleam in the Inspector’s eyes at that, but paid no particular heed to it at the time.

Now, as Grant stood in the corridor of the great space-flier, listening intently for further sounds from his hidden foe, it flashed on him. Miro knew he was on board. It was a Ganymedan who had treacherously attacked him. The puzzle was slowly fitting its pieces together. But the major piece still eluded him. What would happen to the ship?

As he turned to go back to his room, a ripping, tearing, grinding sound came to his startled ears. It was followed by a sudden swishing noise. Grant knew what that meant. A meteor had ripped into the vitals of the space-flier, and the precious air was rushing through the fissure into outer space. He whirled without an instant’s hesitation and sprang down the long corridor toward the captain’s quarters. If caught in time, the hole could be plugged.

Even as he ran, there was another grinding smash, then another, and another. Good Lord, they must have headed right into a meteor shower. Panels were sliding open, and people, scantily attired, thrust startled heads out into the corridor. Someone called after him, but he did not heed or stop his headlong race. He must get to the control room at once.

Already the air in the corridor was a sucking whirlpool that beat and eddied about him in its mad rush to escape. It sounded like the drumbeat of unsilenced exploders. A meteor shower of unprecedented proportions! In the back of Grant’s mind as he ran, hammered a thought. Every swarm of meteors in the solar system was carefully plotted. The lanes of travel were routed to avoid them. There was no known shower in this particular area!

He collided violently with a strange ungainly figure. In his desperate haste he did not give much heed, but tried to push his way past. The figure turned on him, and then Grant stopped short, an exclamation frozen to his lips. Red unwinking eyes stared out at him from goggles set in a helmet. The body was completely inclosed in lusterless creatoid. It was a Ganymedan in a space-suit!

Grant saw the quick movement of the other toward an open side flap. He did not hesitate an instant. His fist shot out and caught the Ganymedan flush in the throat, while his left hand simultaneously seized the creatoid-covered arm that gripped a pencil-ray. The helmeted head went back with a sickening thud. But the Ganymedan was a powerful brute. Even as he staggered back from the force of the blow, vainly trying to release the pencil-ray for action, his right foot jerked forward. The next moment both were rolling on the floor, twisting and heaving in silent combat. Frightened passengers rushed down the corridor, screaming with terror, half carried along by the hurricane wind, clambering over the combatants in an insane desire to get away, where, they knew not; and still neither relaxed his grip, seeking a mortal hold.

Pemberton was certain that his silent unknown foe held the clue to the mystery he was trying to fathom. He fought on, silently, grimly. The cold creatoid fabric was slippery, but a sudden jerk of an arm, a certain quick twist that Grant was familiar with, and his enemy went limp. Grant’s breath was coming in quick, labored gasps. There was very little air left now. But he did not care. He tugged at the fastenings on the helmet. He must see who his captive was, wrest from him the heart of the mystery.

There came a clatter of feet behind him, a sudden rush of space-suited figures that overwhelmed and passed over him with trampling strides. He was torn loose from his prey, rolled over and over, gasping for air. When he staggered to his feet again, bruised and shaken, the corridor was swept clean of figures. His assailants had carried his opponent away with them.

A wild surge of anger swept through him. More Ganymedans, these rescuers, all accoutered for airless space. They had been carefully prepared for this. Heedless of all else, he swayed groggily after them, intent only on joining battle once again. The illumination was dim now, the cries of fear that had rung through the ship were gone; only a deathly silence reigned now. His lungs were burning for want of air; even the whirlwind had died down for lack of fuel. But still he kept on, like a bloodhound on the trail.

He rounded a corner. A slight figure, swaying like a reed, collided with him and would have fallen if he had not thrust out a supporting arm. It was a girl. Even in the shadowy light he saw that she was beautiful. Her delicately molded features were drained white, but her deep pooled eyes were level in their gaze, unafraid.

“I’m sorry,” he managed, finding utterance labored, “Are you hurt?”

“Quite all right,” she said, with a wan smile, “if only I had some air to breathe.”

The essential bravery of her touched him. He forgot all about the escaped Ganymedans.

“We’ll have to try some other portion of the ship. Maybe some of the bulkheads are uninjured.”

She shook her head. “I just saw the captain,” she enunciated faintly. “Every bulkhead is riddled. Said--I--should get space-suit--in stateroom--though no use--doomed. Something wrong--wireless--not working...” Her voice trailed. She had fainted.

Grant caught up her slight form and lurched unsteadily into the nearest cabin. The blood was roaring in his ears now, his heart was pumping madly, but he forced himself on. His eyes strained toward the compartment where the emergency space-suit was neatly compacted. Thank God. It was still there. The inmate had evidently rushed out at the first alarm to join the terror-maddened crush.

Pemberton worked with feverish haste. Somehow he thrust the unconscious girl into the suit, tightened the helmet into position, opened the valve that started the steady measured flow of life-giving oxygen. Then, with dark spots dancing before his eyes, he deposited her gently on the floor, and managed to force himself in the now almost total darkness toward another room.

His swelling hands fumbled. The compartment was empty. Despairing, conscious only of a desire to lie down, to rest, he tried another. It, too, was empty. He stumbled over sprawled bodies, fell, managed to get up again. Again he fumbled into a compartment. The clammy feel of the creatoid never was more welcome. His breath was coming in whistling gasps. It seemed ages of strangulation before the first cool rush of oxygen expanded his tortured lungs. For a full minute he stood there, inhaling deep draughts. Then once more he was himself, his brain functioning with keen clarity.

He must find the Ganymedans and come to grips with them. There was no doubt in his mind that somehow they had been responsible for the cataclysm. Just how, he did not know, but he would find out.

But the girl. He could not leave her. Duty and something else stirred into conflict. He hesitated. In the flap of the suit was an emergency flash. Throwing the beam on the walls and flooring, he managed to retrace his steps to the cabin where he had left her. As he flashed it inside, his heart gave a great bound. She was standing now.

“Feel all right?” he spoke into the tiny transmitter that was part of the regulation equipment.

“Fine.” Her warm, rich voice spoke in his ear. “But I’m not thinking of myself. Are the others on board safe? What happened?”

“I’m afraid we are the only ones alive,” he told her gravely. “As to what happened, I can only guess. We seem to have hit an unusually heavy meteor shower that riddled us through and through, though--” He paused.

“Though what?”

He ignored her question. “The first thing we’ve got to do is find out where we are.” His flash sought the window switch and found it. He went over and pressed it. A section of the beryllium-steel casing slid smoothly open, disclosing a thick flawless quartzite port. He stared out at the dark pattern of space. Long he gazed, then a stifled exclamation reached the girl.

“What is it?” she cried.

“Come and look,” he told her gravely, and made room for her.

At first she saw only the unwinking stars of space. Then her eyes shifted forward. Jupiter lay ahead, a vast cloud-girt disk. It was ominously near. Somehow it gave the effect of rushing straight at her.

Right along the equator floated, or seemed to float, a huge red oval--the Great Red Spot of Jupiter. She had heard of it before. But what caught her immediate attention was a tiny flare of intense illumination, right in the very heart of the Spot. Bright orange it was, tinged with yellow, dazzling even at this distance. She watched it eagerly. Then she gave a sudden start.

“You’ve seen it.” Grant’s voice sounded quietly in her helmet.

“Yes. Why, it--it pulsates!”

“Exactly. Now look along the hull of the ship.”

She did so, and gasped again. The steel-shod sides were bathed in an unearthly orange glow.

“Why, that must be the light from the orange spot down there.”

Grant nodded. “Yes, and more than that. They are power waves of a nature that we’ve known nothing of before. We are being pulled down along that beam straight for Jupiter, straight for the source of that light!”

“But that means there are intelligent beings on Jupiter.”

“No doubt.”

“But--but everyone know that there’s no life on Jupiter. It’s a frozen waste swathed in impenetrable whirlwind clouds.”

“How does everyone know?” Grant retorted. “Has anyone ever penetrated through those clouds?”

“No,” she admitted; “though there have been plenty of expeditions that tried, and never came back.”

“That of course doesn’t prove anything. Mind you,” he added. “I didn’t say there was native life existing on Jupiter. I merely said there were intelligent beings operating that illumination.”

“Who could it be then?”

“We’ll find out when we get down there.”

The very calmness of his matter-of-fact statement brought her back abruptly to their precarious situation.

“But, great heavens, we’ll smash and be killed. Can’t we do something?”

“We’ll not smash.” Grant said positively. “Though very likely we shall be killed. As for doing something, we can only wait and take our chances, if the gentry who are hauling us in will only give us an opportunity. You know,” he added with a fine inconsecutiveness, “I don’t even know your name.”

She bubbled with sudden laughter. “Nona--Nona Gail. I was on my way to Callisto, to meet my father,” she explained. “He’s an engineer, doing some construction work for Interspace Products. But now that I’ve told you all, what and who may you be?”

He was frank. There was now no need for concealment. “Grant Pemberton, an unimportant unit of the Interplanetary Secret Service.”

“Then you knew that the trip would be dangerous,” she challenged.

“Yes.”

“Why did you come?”

“It is part of my duties.”

There was silence between them. He turned to stare out of the quartz port-hole again. Jupiter was perceptibly nearer; an enormous, convex globe that blotted out half the heavens. They were being drawn at a frightful velocity toward the mysterious pulsating point, now blinding in its brilliance.

They both saw it simultaneously: a space-suited figure, far out in the depths of interstellar space, caught up in a sudden flare of orange illumination. The strange figure seemed to whirl around, straighten up, and shoot at breakneck speed headlong for Jupiter. Behind it, and in a direct line with the winking flame in the Great Spot, another space denizen glowed luridly, startlingly, out of the blackness beyond, whirled, and shot down the long invisible path.

Nona cried out: “Grant, tell me quickly, what are they; what is pulling them?”

Even as she spoke, more and more figures were blazoned in that orange ray, until a long file of beings were catapulting in a single straight line past the space-ship, outdistancing it until they became faint specks in the distance.

Pemberton’s hand was upon her shoulder, his eyes literally blazing through the goggles, while his voice shouted in her ears. “Come with me: We haven’t a second to lose.”

“But,” she gasped, “you haven’t told me--”

“No time,” he interrupted, and, shoving her in front of him, he rushed her through corridor after corridor until they came to the air-lock of the liner.

“If only we have time,” he groaned, and cursed himself for a bungling fool for not having surmised the maneuver earlier.

Just as he had expected, the great lock was open. The ship was as silent as the grave. There was no air anywhere, only the unutterably cold airlessness of space. Without pausing in his headlong rush, he pushed the bewildered girl through the open port, out into the overwhelming, intangible blackness. Nona’s smothered cry of fear came to him as the next instant he stepped forward and left the solid footing to float in sudden weightlessness in a vast sea of nothingness.

The girl reached out and caught his arm convulsively. Even through the fabric of their suits he could feel her trembling. Pemberton had taken good care to retain a hold on the edge of the open air-lock. The two swung unsteadily.

“What is the reason for this?” Grant sensed, rather, than heard, the tremor in her voice. She was making a desperate effort to control herself. “We’ll be lost--out here in space.”

“Don’t worry,” he said soothingly. “I’ll explain in due course. In the meantime you’ll have to trust me. Did you see where that invisible ray held when it illumined the last Ganymedan?”

“Ganymedan?” she echoed in surprise. “What makes you think--”

“Never mind that. Did you?” he insisted.

“Yes,” she admitted, “it was about over there.” She indicated the spot with an outthrust arm. “About a hundred yards, I should judge.”

“Exactly,” he agreed. “Well, young lady, our lives, and far more, depend upon our reaching that exact line in space immediately.”

“I don’t know what you are talking about, but even so, how can we make it? I’m not a rocket.”

“It’s difficult, I admit, but we must. Now hold on tight to my arm, and press your feet firmly against the wall of the ship.” She obeyed.

“Now when I count three, shove off violently, and pray that we’re going straight. Are you game?”

She stiffened; then, very slowly, “All right; start counting.”

“Good girl,” Grant said approvingly. “One--two--th-r-ee-ee!”

They flexed their legs in perfect unison. And shoved off.

Out into the blackness of space they shot, lost to all sense of motion: yet the hull of the space-flier, dimly gleaming in the thin light of the far off sun, retreated from them with terrifying swiftness.

They were alone in space! It was an uncanny, a horribly helpless sensation. All about them was infinity, a vast void out of which peered at them the cold, unwinking stars. They were like swimmers in mid-ocean, without even the buoyant feel of the salt water to comfort them.

Nona’s grip on Grant’s arm was agonizing in its intensity.

“Scared?” Grant queried.

“A--a little,” she admitted; “but don’t bother about me. I’m all right.”

She could be depended upon to keep up her end, Grant thought admiringly.

On and on they floated in the welter of space. And still there was no ray, nothing but unrelieved blackness. Pemberton was somewhat worried. Had the saving ray been quenched at the source? Were they too late? If so, they were doomed to a frightful obliterating fall to the surface of the planet, or worse still, they were destined to swing endlessly in space. Already the liner was far away, out of their grasp, even had they desired to return.

His breath was coming in quick gasps now. “Scared?” he once more asked the silent figure beside him.

“Frightfully--but carry on. We’ll get there, wherever it is.”

Her gay determination strengthened him wonderfully. On and on they floated.

Suddenly the dim, dark bulk of the girl caught the uncanny orange light. The next instant the creatoid fabric of his own suit caught it, too.

“Thank God,” he cried joyously. “It’s still on. Just relax, Nona, the ray will take care of us now.”

He felt a powerful tug at his body, he was whirled completely around, and then there was a steady pull. He was being catapulted down the ray to the mysterious point of brilliance in the Great Red Spot. The girl was right beside him. The space-liner was passed with a smooth rush, and soon receded to a dwindling speck.

“Now will you explain?” asked Nona impatiently, after she had caught her breath in sudden relief.

Grant stretched luxuriously before he began.

“Certainly. There’s nothing for us now to do but wait until we get pulled down to Jupiter, and that’ll take some time. I hope we look like Ganymedans.”

“Will you get on with your story!” she cried.

He obeyed. He started from the beginning and went right up to the time when he had so rudely thrust her out into space.

“You see,” he explained. “I had put the puzzle together a bit, but there were still pieces missing. For instance, those chaps down there know that every space-liner is equipped with emergency space-suits. Why pull the ship down with live men on board? That would naturally mean a fight, and we have no mean weapons, what with disintegrator ray-projectors and explosive electro-bullets.” Then, again, for some reason, there were Ganymedans on board. They would very likely be whiffed out in the mêlée. The ship might be destroyed also, and they evidently are very careful about getting the ship down intact. The little meteor holes can easily be plugged up, and the liner made as good as new. At least that was my guess.

“I was trying to puzzle it out, rather hopelessly,” he continued, “when I saw the ray out in space pick up those floating figures. That was the last little piece in the jigsaw.

“The Ganymedans evidently had to leave the ship because, as it approaches the planet, something will be done to kill off any unfortunates who are still alive, waiting their chance to fight the invisible enemy. Possibly a penetrating lethal gas that will be forced into the interior. So they evolved the ray to carry the Ganymedan passengers down gently, safely. And we are stowaways,” he concluded grimly.

Nona had listened intently to the long recital.

“But why,” she expostulated, “was it necessary to have their own people on board? The meteors that riddled the ship were projectiles shot from their station on Jupiter. So was the attraction-ray that pulls the ship down.”

“Because they required a sufficient force to disable the radio apparatus. All radio waves used on interplanetary liners are shielded from interference. It is impossible to blank them out. And with the radio intact, every battle flier in space would be on their trail in a hurry.”

Several hours passed, and still they fell endlessly through space, unaware of their motion except that Jupiter was now a huge orb blotting out the universe. The grim face of the giant planet was enswathed in endless billowing clouds. No one had ever penetrated to the real core. But what held their eager, straining attention was a vast blood red disk, cyclonic in character, directly beneath them. The Great Red Spot! And immediately in the center of it was the tiny, blindingly brilliant yellow orange oval, winking up at them with quick, steady pulsations.

“What can it be?” Nona wondered.

“The source of their power, evidently. But what interests me more just now is where the Ganymedans have their hangout in those clouds, and what they’re doing with the ships they capture.”

Jupiter was now a flat level stretch that reached on all sides as far as the eye could see. Grant felt a sudden sensation of weight again, as though something was pressing with crushing force against his chest.

“Hello,” he said, “our fall is being checked. They’re making sure their friends come to no harm.” And he laughed bitterly, thinking of the men and women lying with lungs ruptured, cold and stiff, in the interior of the Althea; of the possible few wretches who had managed to huddle into space-suits, ignorant of the deadly gas that was soon to search out their seemingly impenetrable habiliments.

Slowly, ever more slowly, they fell. Thin wisps of reddish vapor rushed upward toward them, and then they were enveloped in vast swirls of cloud masses. They were within the Great Spot!

Then the lurid clouds parted suddenly, revealing a deep hole, at the bottom of which flamed and flared the mysterious yellow-orange brilliance. Down the long shaft they fell, while all around its invisible walls dark red cyclones stirred and beat in vain.

Just as it seemed as if they were doomed to fall headlong into the blaze, they were swerved violently into an opening that angled off from the main shaft. Down this branching shaft they continued to fall--interminably--when suddenly it widened, and they were dropping through the interior of a great dome of which the arched roof was the swirling clouds they had just penetrated. Directly beneath floated a flat island of smooth rock, supported and upheld by a shining sea of vapors.

The girl exclaimed sharply, but Grant only nodded to himself with grim satisfaction. He had expected something like this. For, clustered in serried rows at the end of the island directly beneath them were sleek, stream-lined grayhounds of the interplanetary traffic lanes, now resting immovably on the smooth gray stone--the missing space-liners!