When the rolling thunder of infra-bass first came to their ears, Robert Blake and Helen Lawton were standing on the platform of a New York subway station waiting for the arrival of an uptown express to bear them to their homes.

They made a strikingly attractive couple as they stood there. New York had not had time as yet to remove the bronze tan of an outdoor life from Blake’s ruggedly good-looking face. His tall athletic figure was still conspicuous for the lithe strength that had made him an All-Western tackle less than two years ago.

Standing beside Blake’s husky figure, Helen Lawton looked like a tiny, very perfect, blonde doll, with an exquisitely molded face framed in curly bobbed hair that was the clear golden-amber hue of orange honey. There was a diamond sparkling on the ring finger of the girl’s slim left hand, placed there by Blake.

It was well after midnight, and the only other passenger waiting on the station was a burly chap leaning against one of the white pillars on the other side of the platform. After a casual glance at the fellow, with his derby hat shoved far back from a low forehead, his blatantly conspicuous clothing, and the suspicious bulge under one arm-pit, Blake had mentally set him down as a minor gangster, probably a strong-arm man for some beer mob.

Blake and Helen had been standing there but a few minutes when the strange sound first became audible. For a moment Blake thought it was merely the rumbling roar of an express approaching far down the tunnel. Then he realized that no subway train could possibly produce a sound effect so oddly disturbing and strangely alien.

It was like no sound that Blake had ever heard before. Vibrant with colossal power, it suggested a sustained note struck from a giant organ, a note so low in pitch that it seemed a full octave below the lowest bass note ever struck. Whatever it was, the thundering vibration of infra-bass was coming nearer with startling swiftness.

It was impossible to locate the source of the mighty pulsing note. It seemed to be coming simultaneously from all directions, like a great hollow sphere of invisible sound waves closing in with the station platform as its central focal point.

Helen’s face was white with dread as she shrank closer into Blake’s embrace. Blake noted that the gangster across the platform was standing tensely at bay with his back against the pillar and his right hand thrust under his coat as he stared wildly about him in an effort to discover the cause of the disturbance.

The rolling thunder closed in upon them with a final rush that brought it so near that their very bodies seemed to vibrate in harmony with that mighty note of shuddering bass. Then with startling abruptness the green net came.

Out from the walls and down from the roof spurted scores of quivering ribbons of blinding green flame. Swiftly the radiant tendrils rushed in upon the shrinking three from every side, while the infra-bass thundered in mighty crescendo.

Blake instinctively swept Helen close within the shelter of his arms in an effort to protect her with his own body against the searing menace of those onrushing green flames. The next moment the fiery ribbons were upon them, lashing about their bodies, crossing and crisscrossing in the air above and around them in a great tangled web of interlacing lines of flame that filled the entire platform.

With a shock of relief Blake found that there was no heat in those strange flames, but his relief was short-lived as the next second brought him realization of the real menace of the radiant ribbons. There was a solidity and strength in those glowing streamers that held them as helplessly captive as though they were gripped in ribbons of steel. Dazed and helpless, the three struggled for a moment in the meshes of the weird net of flame like fish caught in the strands of some giant cosmic seine.

The trembling thunder of infra-bass abruptly changed to a thin whining note so high in pitch that it seemed the nearly soundless ghost of a metallic scream. With the change in sound Blake became aware of a new and astounding change in his surroundings.

The walls and roof of the station seemed closing in upon him as though he were growing in size at an incredible rate. The next moment he shot through the roof, hurtling on and upward with the velocity of a rocket. The sensation was one that his reeling brain could not even grasp. His body seemed to be inside every stone, iron bar, and lump of earth, yet at the same time every exterior object seemed within his body. It was an eery chaos of a dozen different dimensions blending to form a Space in which there was no known dimension.

As they flashed on out to the surface Blake had one hazy glimpse of Manhattan’s glowing lights spread all about them. Then the speed of their progress leaped into a new and terrible acceleration that blotted out every tangible sensation from Blake’s brain.

Time and Space alike seemed to vanish as their hurtling flight sent them rocketing on for distances inconceivably vast through a bleak and appalling Nothingness, where neither sight nor sound existed.

Then abruptly the speed of their flight seemed to be lessening. Sensation returned to Blake. He again heard the thin high-pitched metallic wail, now swiftly deepening to the familiar growl of rolling bass. He again noted the presence of the glowing green ribbons of the net that still encircled them.

A blindingly brilliant purple mist was now closing in upon them from every direction, bringing with it a nameless and agonizing force that seemed to be shaking the very atoms in Blake’s body asunder. Then they dropped swiftly down out of the purple mists, and the strange agony at once vanished. Blake felt their downward progress come to an end with the gentle arrival of his feet upon firm ground.

The encircling net of green flame glowed dazzlingly brighter for a brief moment, then swiftly vanished into thin air, while the mutter of bass vibrations simultaneously died away into silence. Blake staggered and nearly fell as the sudden release from the net’s strands again left his body free.

He looked down at Helen as she stood huddled close beside him, still in the shelter of his arms. The girl’s face was white with terror as she looked back up at him.

“Bob, what happened--and where on earth are we?” Her voice trembled a little in spite of her plucky effort to keep it steady.

Blake’s bewildered gaze was already roving around them trying to comprehend the incredible details of their surroundings. “I’ve no idea what happened, dear,” he answered slowly. “As to where we are now, I’m very much afraid it’s nowhere on Earth!”

“Then where is this hopped-up layout anyway, fellah, if it ain’t on Earth?” broke in a voice with a decided East Side twang. Blake quickly turned and saw that the gangster had remained with them in that eery flight in the green net. There was an expression of dumfounded amazement upon the man’s heavy face, and he was obviously anxious to be friendly with the two who now represented the only link with the familiar world he had known.

“Gee, for a minute I thought they had me on the spot in some new way, sure!” he chattered excitedly as he came quickly over to join Helen and Blake. “There’s plenty of guys wantin’ to turn the heat on me there in the Big Town. I’m Gil Mapes, see? But this ain’t no frame-up like any I ever heard of. What happened anyway, fellah?”

For the moment Blake did not answer. The three of them were silent as they stared about them with eyes that were dazed by the startlingly unfamiliar aspect of every detail in their surroundings.

From the twin purple suns that blazed down through the tenuous mists overhead to the barren blue-gray ground underfoot, there was not a single object familiar to Earthly eyes. The huge enclosure in which the three of them stood was obviously the work of intelligent beings of some kind, but its mechanical details were products of a science different from any known to Blake.

The purpose of the enclosure seemed to be to maintain an area of clear air in the midst of the swirling purple vapors that pressed in against it from the top and from every side. In shape it was a great oblong cell, some fifty feet high, two hundred yards long, and about one hundred yards wide. The three captives stood near the center.

Fencing in the enclosure at twenty-yard intervals and reaching upward to the ceiling were slender posts of some lusterless black metal. Between these posts streamed unbroken, nearly transparent sheets of some unknown force, the only visible sign of which was the presence of countless millions of tiny shimmering golden flecks which danced like dust motes in a ray of sunlight. It was obviously this thin sheet of unknown force that was keeping the purple mists at bay, for fan-like antennae at the top of each post spread a similar shimmering sheet that formed a ceiling for the clear-aired area.

The three Earthlings were facing one of the side walls of the big enclosures. The purple mists outside made it hard to see clearly for any distance, but Blake had an impression that the surrounding terrain was featured by the same barren, nearly desert bleakness that characterized the interior of the enclosure, where scattered clumps of dead, spiky black branches of shrub-like vegetation were the only sign of plant life.

Just within the distant end wall at their right there was a low platform surmounted by a wide arch some ten feet in height, both constructed of silver-colored metal. There was nothing between them and the end wall to their left, but they could see that the ground sloped sharply upward from the barrier-sheet, and on the crest of the ridge a gigantic cone-shaped structure of solid black could be seen dimly through the intervening mists.

The cone-building seemed to be the source of the power that kept the enclosure intact. Slender cables of black metal ran down the slope from it into the clear-aired space, spreading out over the dusty gray-blue ground to the base of each of the tall posts, with a heavier copper-colored cable running on the silver arch. From within the windowless interior of the cone there was audible a low hum as of tremendous power being generated there.

“Gee, what a rummy joint this place is!” There was frank awe in the gangster’s voice as he at last broke the silence. “That guy with the green net sure took us for one sweet ride. Mebbe we’re on the Moon now, or on Mars, huh?”

Blake shook his head. “No, we’re completely out of our entire solar system. Those twin purple suns up there prove that. We may even be in another universe, or another dimension from our own. A piece of apparatus that could whisk us up through fifty feet of earth and masonry as that green net did obviously works in dimensions of which we’ve never dreamed. The only thing we’re sure of is that we were brought to this purple world deliberately and intentionally by an intelligent being of some kind, scooped up like tadpoles from a mud-puddle and dumped here in this elaborate enclosure It had already prepared for us.”

Blake nodded to where the black cone-building loomed through the purple mists outside the end wall. “Whoever or whatever the thing was that brought us here, I have a hunch It’s there in that power-house watching us. I’d suggest that we walk down toward that end of the enclosure for a closer look. We may at least find out whether we’re guests or prisoners.”

“Listens good to me, fellah,” agreed Mapes, sliding a hand up to his shoulder holster and bringing out a squat black automatic pistol of heavy caliber. “We’ll do a prowl, over that way, and if His Nibs tries any more funny business mebbe a few slugs outta this rod will change his mind for him.”

“Better go easy with the gun, Mapes,” advised Blake as the three of them started slowly toward the cone-building. “From what we’ve already seen, there must be weapons in this world that would make your pistol look like a kid’s pop-gun. We’d better go easy till--wait, what’s that?”

The thin high-pitched whine, followed promptly by the familiar growling thunder of infra-bass, had again become audible. At the same moment a long pencil-like beam of green light glowed into visibility, extending from the tip of the cone to a point high within the enclosure just back of them. As they halted abruptly and watched, they saw the interlacing meshes of the green flame-net materialize suddenly at the end of the beam.

The beam curved into an arc that dropped the net swiftly to the ground some thirty yards from them. Its meshes were packed nearly full of dark, writhing figures.

“Looks like some more tadpoles arriving for our pond!” Mapes exclaimed. “I wonder what part of N’ Yawk His Nibs yanked these babies from?”

Blake’s answer died on his lips as the net and beam glowed blindingly brighter for a brief second, then disappeared, leaving the dark figures in full view. Helen choked back a gasp of horror. Mapes swore in consternation and hurriedly swung his pistol into line with those writhing shapes.

The net’s latest captives were not from New York, nor were they from any other part of the planet Earth. Hideous spawn of some unknown world out in the black void of Space, they writhed for a moment in a nightmare chaos of countless brown-furred bodies, then swiftly disentangled themselves before the staring eyes of the three Earthlings.

The things were apparently too low in the mental scale to have any reaction to their situation other than a blind instinct to attack any other living being within reach, for they promptly headed for the three captives from Earth.

As the creatures came shambling rapidly forward on powerful bowed legs, and with the tips of their long hairy arms brushing the ground, they looked like grotesquely distorted apes. The crowning horror of those shambling figures, however, lay in the fact that they were completely headless!

Even when the things approached to a distance of less than ten feet before halting in momentary indecision, Blake could detect no sign of any normal skull in the blunt space at the top of the powerful hairy torso. There was a furry-lipped mouth opening of some kind in the hollow between the bulging shoulders, but of eyes, ears, nose, or brain cavity there was no discernible trace.

For a long moment the headless ape-things and the three human beings stood silently facing each other. Mapes’ pistol was leveled pointblank at the nearest of the creatures, but their overwhelming numbers made the gangster hold his fire.

There were two distinct groups of the things. At least twenty members of each group were in the crowd facing the Earthlings. To the rear of these attackers two oddly repulsive objects were carried and carefully shielded by picked guards of four unusually large and powerful ape-things.

The nature of those two guarded objects puzzled Blake. They looked like large eggs of dirty-gray jelly, about a yard in length. They were obviously alive, for their gelatinous masses quivered and trembled in constant activity. Blake noted that there seemed to be a curious connection between the ebb and flow of pulsations in the egg-masses and the movements of the ape-things.

His attention was abruptly recalled to the headless things in front of him as they suddenly began shambling forward again. There was no possible mistaking the intention of those advancing horrors. They were moving to the attack.

They reached barely to Blake’s shoulders, but he realized that their enormous numbers and hook-taloned hands would make the result of the battle almost a foregone conclusion. The fact that the headless things were without eyes was no handicap to them. The swift certainty of their movements proved that they had a sense of sight of some kind that was in every way as efficient as eyesight.

Blake looked hurriedly around him, seeking a place where they might be at the best possible advantage in the impending battle. There was a small dense thicket of the spiky dead branches half a dozen yards to their right. At Blake’s low command, the three made a dash for the thicket. Arriving there, they ranged themselves against it, with their backs at least partially protected from attack.

The maneuver seemed to puzzle the ape-things for a moment. They stood passively watching the retreat of the three until they had reached the thicket. Then the creatures again began slowly closing in upon them. Blake snatched up a dead branch from the ground near the thicket, and was delighted to find that its weight and tough fiber made it an excellent club.

He stripped off his topcoat and passed it back to Helen. Its tough fabric, heavily rubberized for proof against rain, might guard her head and face at least momentarily from those ripping talons if the headless attackers came to close quarters. With Helen safely behind them, Blake and Mapes turned grimly to face the enemy.

The attack was prompt in coming. Moving with the perfect synchronization of a single unit, one of the main groups came shambling in, followed an instant later by the other group. Mapes’ pistol sent a bullet crashing squarely into the nearest attacker. The creature staggered momentarily, then came lurching on again, apparently not even crippled. Blake swung his heavy club in a whistling arc that sent two of his adversaries broken and writhing to the ground.

He heard Mapes’ pistol bark four times more as the things closed in. Then the gun was knocked from the gangster’s grip by a groping talon-armed hand. Mapes tried to batter back his assailants with his naked fists, but the flailing arms of the horde knocked him from his feet. His limp body was promptly tramped into unconsciousness by the milling feet of the close-packed group.

Blake lashed the heavy club about him with a burst of savage fury that for the moment sent the furred horrors reeling backward. Their retreat ended after a scant two yards. Reforming their ranks, they again began cautiously shambling forward in a new attack that Blake realized would probably mean the end.

It was easy enough to batter the things to ground, but it seemed impossible to seriously hurt them. Their incredible vitality and their overwhelming numbers made them almost invincible. Grimly Blake set himself to battle as long as he could in that last desperate effort to keep the hordes at bay.

He noticed idly that the two groups still kept their oddly separated formation. Behind them the two egg-masses of jelly were now seething in new activity after a brief lessening of their gruesome shivering. Blake now saw that there was a direct and unmistakable connection between the activity of the jelly and the corresponding activity of the ape-things.

Realization of the fact sent a sudden flash of inspiration flaming through Blake’s weary brain, correlating the real significance of a dozen different things he had been subconsciously noting ever since the first appearance of the weird beasts.

Those attacking things were not hordes of individual animals. They were merely two complete organisms, with the members of each organism controlled by its nucleus through invisible lines of nervous force as the various individual cells of the human body are linked by nerve fibers. No wonder the creatures themselves were blind. The egg-mass that was the nucleus of each of the two groups was eyes, brain, and seat of life for every ape-thing in the group.

With a swift surge of hope Blake realized the way to conquer the things. If he could only shatter those flaccid masses of jelly, he would destroy the swarming dozens of beasts at the same time.

Reaching the jelly ovoids seemed at first consideration to be an impossible task. They were carefully guarded far in the rear of the attacking groups. Blake knew that he had scarcely a chance in a hundred of battering his way through the intervening ape-things.

Then he remembered the gangster’s pistol. His searching eyes found it immediately, there on the ground nearly under the feet of the ape-things as they again shambled forward to the attack.

Blake staked everything upon a last desperate sortie against the advancing things. With his club whistling around his head in crashing blows that wrought murderous havoc in the close-packed hordes, he drove them back for one breathless moment that gave him time to leap forward and snatch up the pistol.

The ape-things were already springing back upon him as he swung the pistol into line with one of the jelly-masses. He barely pressed the trigger before the charging brutes knocked him from his feet.

As he went down he flung his arms over his head to protect his face from the expected attack of those hooked talons, but none came. A body thudded down upon him, then slid limply off again without making any move to attack. Blake scrambled to his feet.

Writhing upon the ground all around him were ape-things in their death agonies. On the ground beyond them, quivering and broken in the midst of its dying guards, was a viscid mass of loathsome gray jelly. Blake’s shot had apparently struck home squarely in the center of that vulnerable blob. Even as he watched, the gelatinous mass shuddered in a last convulsion, then became quite still. At the same instant the last sign of life vanished from the writhing ape-things on the ground.

A good half of the attacking creatures were included in the dead bodies. The other half, Blake now saw, had retreated to cluster in wild panic about the remaining blob of jelly. Realizing exultantly that his single shot had slain one of the two weirdly disassociated organisms, Blake with pistol in hand advanced toward the other, trying to get a clear shot at the jelly through the furry bodies clustering around it.

The group promptly turned and fled in blind panic. Blake sent the pistol’s last shot crashing into the mass without any appreciable effect. Then the things’ stampede carried them hurtling on through one of the gold-flecked side walls out into the swirling purple mists.

The gold-flecked sheet flowed together again so swiftly behind the things that a fraction of a second later there was not even the slightest indication in its shimmering unbroken surface to show that it had ever been pierced.

For thirty yards the fleeing ape-things sped on into the purple vapors. Then disaster struck them with bewildering swiftness. They stopped in full flight, shuddered for a moment, then slumped to the ground with their limbs writhing in agony. In their center the jelly ovoid quivered madly in the same strange torture.

Tiny patches of vivid purple appeared at a hundred different points upon the dying creatures. The patches spread and merged with lightning rapidity until a solid sheet of livid purple covered the writhing mass. Swiftly that mass lost both movement and shape as it melted down into a pool of turgid purple slime. Then the slime vaporized into purple mists that blended into the surrounding vapors, and all trace of the ape-things and their jelly nucleus had vanished.

Stunned by the incredible speed of this general dissolution, Blake realized for the first time the real reason for the presence of the gold-flecked walls of force. Without those shimmering walls the captives would not have lived for a minute in the deadly purple atmosphere of this weird world beneath the twin suns. The gold-flecked walls were both their protection and their prison. The swirling purple mists outside those walls held the Earthlings as effectively and hopelessly prisoners in their enclosure as gold-fish in a bowl of water.

Blake turned back to the thicket to see how Helen and Mapes had fared in that terrific battle with the headless things. He was relieved to see that the girl had apparently escaped without even a scratch. She was kneeling beside Mapes’ prone figure, doing what she could to revive him. The gangster was badly battered, but he seemed to have no serious injuries. He was already beginning to stir weakly and show signs of returning life.

Blake started to step over to the two. Then he stopped abruptly as he heard a sharp metallic clang from the cone-building out in the purple mists beyond the end wall. He looked quickly up and saw that an oval window had opened in the structure near its tip. Framed in the opening was what seemed to be a large concave mirror. At one side of the mirror was a living being of some kind, but the intervening mists prevented Blake from making out any details beyond a hazy glimpse of a cluster of what seemed to be long slender snake-like black tentacles.