Despair gripped Dixon for a moment. Then he remembered the unbroken head-piece of the slain monster. True, the glow of its globe was opalescent instead of white, but it seemed to offer its wearer the same immunity to the green moon's rays.

He swiftly retrieved the head-piece from the spider-creature's body, and set the light metal framework in place on Ruth's auburn curls.

Results came with incredible quickness. The rigidity left Ruth's body immediately. Her breath came in fast-quickening gasps, and her eyes fluttered open as Dixon knelt over her.

"It's Bruce, Ruth--Bruce Dixon," he said tenderly. "Don't you know me, dear?"

But there was no trace of recognition in those wide-open blue eyes staring fixedly up at him. For a moment Ruth lay there with muscles strangely tense. Then with a lithe strength that was amazing she suddenly twisted free of the clasp of Dixon's arms and sprang to her feet.

The next minute Dixon gave ground, and he found himself battling for his very life. This was not the Ruth Lawton whom he had known and loved. This was a madwoman of savage menace, with soft lips writhing over white teeth in a jungle snarl, and blue eyes that fairly glittered with unrestrained, insensate hate.

He tried to close with the maddened girl, but instantly regretted his rashness. Her slender body seemed imbued with the strength of a tigress as she sent slim fingers clawing at his throat. He tore himself free just in time. Dazed and shaken, he again gave ground before the fury of the girl's attack.

He could not bring himself to the point of actively fighting back, yet he knew that in another moment he would either have to mercilessly batter his beautiful adversary into helplessness or else be himself overcome. There was no middle course.

Then old Emil Crawford's voice came again as the old man rallied to consciousness for another brief moment.

"Bruce, the opal globe is a direct link to those devils themselves! Break it, Bruce, break it--for Ruth's sake as well as your own!"

Crawford had barely finished his gasped warning when Ruth again hurled herself forward upon Dixon with tapering fingers curved like talons as they sought his throat. Dixon swept her clutching hands aside with a desperate left-handed parry, then s.n.a.t.c.hed wildly at the gleaming head-piece with his right hand.

The thing came away in his grasp, and in the same swift movement he savagely smashed it against the rocky wall beside him. Whatever the opalescent globe's eery powers might be, it was not indestructible. It shattered like a bursting bubble, its fire dying in a tiny cloud of particles that s.h.i.+mmered faintly for a moment, then was gone.

Again, the effect upon Ruth was almost instantaneous. Every trace of her insane fury vanished. She swayed dizzily and would have fallen had not Dixon caught her in his arms. For a moment she looked up into his face with eyes in which recognition now shone unmistakably. Then her eyelids slowly closed, and she again lapsed into unconsciousness.

Dixon looked over at Emil Crawford, and found that the old man had again collapsed. Dixon knew of but one thing to do with the stricken man and girl, and that was to take them to his laboratory. The laboratory, apparently insulated by veins of lead ore in the mountain surrounding it, was the one sure spot of refuge in this weird nightmare world of paralyzing lunar rays and prowling monsters.

Flinging his tunic over Ruth's head to s.h.i.+eld her as much as possible from the moonlight, he carried her to the laboratory, then returned for Emil Crawford. Safe within the subterranean retreat with the old scientist, Dixon removed his enc.u.mbering lead costume and began doing what he could for the stricken pair.

Ruth was still unconscious, but the cataleptic rigidity was already nearly gone from her body, and her breathing was now the deep respiration of normal sleep.

Emil Crawford's condition was more serious. Not only was the old man's frail strength nearly exhausted, but he was also badly wounded. His thin chest was seared by two great livid areas of burned flesh, the nature of which puzzled Dixon as he began to dress the injuries. They seemed of radioactive origin, yet in many ways they were unlike any radium burns that Dixon had ever seen.

While Dixon was working over him, Crawford stirred weakly and opened his eyes. He sighed in relief as he recognized his surroundings.

"Good boy, Bruce!" he commended wanly. "We are safe here among the insulating veins of lead ore in the mountain. This is where Ruth and I were trying to come after we escaped from those devils to-night. But, Bruce, how did you guess the radioactive nature of the Green Sickness in time to avoid falling a victim to it as soon as you left the shelter of your laboratory?"

"My escape was entirely luck," Dixon admitted grimly. "To-night I left my laboratory for the first time in three days. I found a world gone mad, with a strange green moon blazing down upon a land of living dead men, and with marauding monsters hideous enough to have been sp.a.w.ned in the Pit itself. What in Heaven's name does it all mean?"

"I am afraid that it means the end of the world, Bruce," Crawford answered quietly. "It was a little over forty-eight hours ago that the incredible event first happened. Without a moment's warning, the moon turned green! Hardly had the world's astronomers had time to speculate upon this amazing phenomenon before the Green Sickness struck--a pestilence of appalling deadliness that swept resistlessly in the path of those weird green rays. Wherever the green moon shone, every living creature succ.u.mbed with ghastly swiftness to the condition of living death that you have seen.

"Westward with the racing moon sped the Green Sickness, and nothing stayed its attack. The green rays pierced through buildings of wood, stone, and iron as though they did not exist. A doomed world had neither time nor opportunity to guess that lead was the one armor against those dread rays. To-night, Bruce, we are in all probability the only three human beings on this planet who are not slumbering in the paralytic stupor of the Green Sickness.

"Ruth and I were stricken with the rest of the world," Crawford continued. "We recovered consciousness hours later to find ourselves captives in the Earth-camp of the invaders themselves. You probably saw the display of lights that marks their camp down in the valley a mile beyond my place. We have learned since that the s.p.a.ce s.h.i.+p of the invaders dropped silently down into the valley the night before the moon turned green and established the camp as a sort of outpost and observatory. They left two of their number there as pioneers, then the rest of them departed in the s.p.a.ce s.h.i.+p for their present post up near the moon.

"Ruth and I were revived only that the two invaders in the camp might question us regarding life on this planet. They have a science that is based upon principles as utterly strange and incomprehensible to us as ours probably is to them. They probed my brain with a thought machine. It was an apparatus that worked both ways. What knowledge they got from me I do not know, but I do know that they unwittingly told me much in the bizarre and incredible mental pictures that the machine carried from their brains to mine.

"They are refugees. Bruce, from a planet that circled about the star that we know as Alpha Centauri, a star that is the nearest of all our stellar neighbors, being only four and a third light years distant. Their home planet was disrupted by a colossal engineering experiment of the Centaurians themselves, the only survivors being a group of fifty who escaped in a s.p.a.ce s.h.i.+p just before the catastrophe.

"There were no other habitable planets in their own system, so in desperation these refugees sped out across the void to our solar system in the hope of finding a new home here. They reconnoitered our Earth secretly and found it ideal. But first they believed that they must conquer the life that already held this Earth. To do this, they struck with the Green Sickness.

"The rays that are turning the moon green emanate from the s.p.a.ce s.h.i.+p hovering up there some fifty thousand miles from the moon itself. The Centaurian's rays, blending with the sunlight striking the disc of the full moon, are intensified in some unknown way, then reflected across the quarter of a million miles to the Earth, to flood this planet with virulent radiance.

"The green moonlight is radioactive in nature, and overcomes animal life within a matter of fifteen minutes or less. The rays are most powerful when the moon is in the sky, but their effect continues even after it has set, because as long as the green moonlight strikes any part of the Earth's atmosphere the entire atmospheric envelope of the planet remains charged with the paralyzing radioactive influence.

"Earth's inhabitants are not dead. They are merely stupefied. If the green rays were to cease now, most of the victims of the Green Sickness would quickly recover with little permanent injury. But, Bruce, if that evil green moon blazes on for twenty-four hours more, the brain powers of Earth's millions will be forever shattered. So weakened will they be by then that recovery will be impossible even with the rays shut off, and the entire planet will be populated only by mindless imbeciles, readily available material for the myriads of monstrous hybrids that the invaders will create to serve them.

"To-night you saw the hybrid that the invaders sent to recapture Ruth and me. It was a fit specimen of the grisly magic which those devils from outer s.p.a.ce work with their uncanny surgery and growth-stimulating radioactive rays. The basic element of that monster was an ordinary tarantula spider, with its growth incredibly increased in a few short hours of intensive ray treatment in the Centaurian's camp. The half-head grafted to it was that of a human being. They always graft the brain cavity of a mammal to a hybrid--half heads of burros, horses, or even dogs, but preferably those of human beings. I think that they prefer to use as great a brain power as possible.

"The hybrids are controlled through the small opalescent globes on their heads, globes that are in direct tune with a huge master globe of opalescent fire in the invaders' camp. When Ruth attacked you after you placed the opal head-piece upon her head, she was for the moment merely another of the invaders' servants blindly obeying the broadcast command to kill. The white globes that Ruth and I wore when we escaped from the camp were identical with those worn by the invaders themselves, being nothing more than harmless insulators against the effect of the green moonlight."

A sudden spasm of pain convulsed Crawford's face. Dixon sprang forward to aid him, but the old man rallied with an effort and weakly waved Dixon back.

"I'm all right, Bruce," he gasped. "My strength is nearly exhausted, that is all. Like a garrulous old fool I've worn myself out talking about everything but the one important subject. Bruce, have you developed that new and infinitely powerful explosive you were working on?"

"Yes," Dixon answered grimly. "I have an explosive right here in the laboratory that can easily blow the Centaurian's camp completely off the map."

Crawford shook his head impatiently. "Destroying the camp would do no good. We must shatter the s.p.a.ce s.h.i.+p itself if we are to extinguish those green rays in time to save our world."

"That is impossible if the s.p.a.ce s.h.i.+p is hovering up there by the moon!" Dixon protested.

"No, it is not impossible," Crawford answered confidently. "I have a projectile in my laboratory that will not only hurtle across that great gap with incredible speed, but will also infallibly strike its target when it gets there. It is a projectile that is as irresistibly drawn by radio waves as steel is by a magnet, and it will speed as straight to the source of those waves as a bit of steel will to the magnet.

"The Centaurians in the s.p.a.ce s.h.i.+p," Crawford continued, "are in constant communication with their camp through radio apparatus much like our own. If you can pack a powerful contact charge of your explosive in my projectile, I can guarantee that when the projectile is released it will flash out into s.p.a.ce and score a direct hit against the walls of the s.p.a.ce s.h.i.+p."

"I can pack the explosive in the projectile, all right," Dixon answered grimly. "We will need only a lump the size of an egg, and a small container of the heavy gas that activates it. The explosive itself is a radium compound that, when allowed to come in contact with the activating gas, becomes so unstable that any sharp blow will set it off in an explosion that in a matter of seconds releases the infinite quant.i.ties of energy usually released by radium over a period of at least twelve hundred years. The cataclysmic force of that explosion should be enough to wreck a small planet."

"Good!" Crawford commended weakly. "If you can only strike your blow to-night, Bruce, our world still has a chance. If only you--" The old man's voice suddenly failed. He sank back in utter collapse, his eyes closed and his last vestige of strength spent.

Knowing that the old man would probably remain in his sleep of complete exhaustion for hours, Dixon turned his attention to Ruth. To his surprise, he found her sitting up, apparently completely recovered.

"I'm quite all right again," she said rea.s.suringly. "I've been listening to what Uncle told you. Go ahead and prepare your explosive, Bruce. I'll do what I can for Uncle while you're working."

Dixon donned his lead-cloth hood and tunic again and set to work. Ten minutes later he turned to Ruth with a slender foot-long cylinder of lead in his hand.

"Ruth, will this fit your Uncle's projectile?" he asked.

"Easily," she a.s.sured him. "But isn't it frightfully dangerous to carry in that form?"

"No, it's absolutely safe now, and will be safe until this stud is turned, releasing the activating gas from one compartment to mingle with the radium compound in the other section. Then the cylinder will become a bomb that any sharp jar will detonate."

"All right, let's go then," Ruth answered. "Have you any more of those lead clothes that I can wear? I could wear the globe head-piece that Uncle wore, but it would loom up in the dark like a searchlight."

Dixon did not protest Ruth's going with him. There was nothing further that could be done for Emil Crawford for hours and in the hazardous sally to Crawford's laboratory he knew that Ruth's cool courage and quick wits would at least double their chances for success in their desperate mission. He provided her with a reserve hood and tunic of lead cloth, then handed her a tiny leaden pellet.

"Keep this for a last resort," he told her. "It's a contact bomb that becomes ready to throw when this safety catch is snapped over. I wish we had a dozen of them, but that's the last capsule I had and there's no time to prepare more."

He fished a rusty old revolver out of a drawer, and placed it in his pocket. "I'll use this gun for a last resort weapon myself," he said. "The action only works about half the time, but it's the only firearm in the place."

The green moon was still high in the sky as Ruth and Dixon emerged from the tunnel, but it was already beginning to drop gradually down toward the west. Dixon wheeled his disreputable flivver out of its nearby shed. With engine silent they started coasting down the rough winding road into the valley.

For nearly two miles they wound down the long grade. Then, just as they reached the valley floor they saw, far up among the rocks to the left of the road, the thing they had been dreading--the bobbing opalescent globe that marked the presence of one of the Centaurians' hideous hybrids. The s.h.i.+mmering globe paused for a moment, then came racing down toward them.

The need for secrecy was past. Dixon threw the car in gear and savagely pulled down the gas lever. With throttle wide open they hurtled around the perilous curves of the narrow road, but always in the rocks beside and above them they heard the scuttling progress of some huge, many-legged creature that constantly kept pace with them.

They had occasional glimpses of the thing. Its pale jointed body was some twenty feet in length, and had apparently been developed from that of a centipede, with scores of racing legs that carried it with startling speed over the rocky terrain.

The flivver raced madly on toward the blaze of kaleidoscopic colors that marked the Centaurians' camp. Crawford's home loomed up now barely a hundred yards ahead.

As though sensing that its quarry was about to escape, the hybrid flashed a burst of speed that sent it on by the car for a full fifty yards, then down into the road directly in front, where it whirled to confront them. Dixon knew that he could never stop the car in the short gap separating them from that huge upreared figure, and to attempt swerving from the road upon either side was certain disaster.

He took the only remaining chance. With throttle wide open he sent the little car hurtling straight for the giant centipede. He threw his body in front of Ruth, to s.h.i.+eld her as much as possible, just as they smashed squarely into the hybrid.

The impact was too much for even that monstrous figure. It was hurled bodily from the road to crash upon the jagged rocks at the bottom of a thirty-foot gully. There it sprawled in a broken ma.s.s, too hopelessly shattered to ever rise again.

The flivver skidded momentarily, then crumpled to a full stop against the rocks at the side of the road. Dixon and Ruth scrambled from the wreckage and raced for Crawford's home, scarcely fifty yards ahead.

They entered the laboratory and Ruth went directly over to where the radio-projectile rested in a wall-rack. Dixon took the gleaming cylinder down to examine it. Tapering to a rounded point at the front end, it was nearly a yard long and about five inches in diameter.

"The mechanism inside the projectile is turned off now, of course," Ruth said. "If it were turned on, the projectile would have been on its way to the s.p.a.ce s.h.i.+p long ago, for the radio waves are as strong here as at the Centaurians' camp."

The girl pointed to a small metal stud in the nose of the projectile.

"When that is snapped over, it makes the contact that sets the magnetizing mechanism into action," she explained. "Then the projectile will go hurtling directly for the source of any radio waves within range. I don't know the nature of its mechanism. Uncle merely told me that it is the application of an entirely new principle of electricity."

Dixon laid the long projectile down on the work-bench, and began packing his lead cylinder of explosive inside it. He had to release the lead cylinder's safety catch before closing the projectile, which made his work a thrillingly precarious one, for any sharp blow now would detonate the unstable mixture of gas and radium compound in one cataclysmic explosion.

He sighed in relief as he finally straightened up with the completed projectile held carefully in both hands.

"All we have to do now, Ruth," he said, "is step out from under this roof and snap that energizing stud. Then this little package of destruction will be on its way to our Centaurian friends up there by that pestilential green moon."

Ruth stepped ahead to open the door for him. With the end of their task so near at hand, both forgot to be cautious.

Ruth threw the door open and took one step outside, then suddenly screamed in terror as her shoulders were encircled by a long snake-like object that came whipping down from some vast something that had been lurking just outside. Dixon tried to dodge back, but too late. Another great hairy tentacle came las.h.i.+ng around his shoulders, pinning his arms tightly and jerking him out of the doorway.

He had a swift vague glimpse of a hybrid looming there in the green moonlight--a tarantula hybrid that in size and horror dwarfed any of the frightful products of Centaurian science that he had yet seen.

Before Dixon had time to note any of the details of his a.s.sailant another tentacle curled around him, tearing the projectile from his grasp. Then he was irresistibly drawn up toward that grisly head where Ruth's body was also suspended in one of the powerful tentacles. The next moment, bearing its burdens with amazing ease, the giant hybrid started off.

Dixon tried with all his strength to squirm free enough to get a hand upon the revolver in his pocket, but the constricting tentacle did not give for even an inch. The only result of his effort was to twist his hood to one side, leaving him as effectually blindfolded as though his head were in a sack.

Long minutes of swaying, pitching motion followed as the hybrid sped over the rocky ridges and gullies. It finally came to a halt, and for another minute or so Dixon was held there motionless in mid-air, dimly conscious of a subdued hum of activity all about him. Then he was gently lowered to the ground again.

While one tentacle still held him securely, another tore away his hood and tunic. Almost immediately the hood was replaced by one of the protective white globe devices. Dixon blinked for a moment in half-blinded bewilderment as he got his first glimpse of the Earth-camp of the Centaurians.

The place, located on the smooth rock floor of a large natural basin, seemed a veritable cauldron of seething colors which rippled and blended in a dazzling maze of unearthly splendor. But Dixon forgot everything else in that weird camp as his startled gaze fell upon the creature standing directly in front of him.

He knew instinctively that the thing must be one of the Alpha Centaurians, for in its alien grotesqueness the figure was utterly dissimilar to anything ever seen upon Earth before.

Life upon the shattered planet of that far distant sun had apparently sprung from sources both crustacean and reptilian. The Centaurian stood barely five feet in height. Its bulky, box-like body was completely covered with a chitinous armor that gleamed pale yellowish green.

Two short powerful legs, scaled like those of a lizard, ended in feet that resembled degenerated talons. Two pairs of slender arms emanated from the creature's shoulders, with their many-jointed flexible length ending in delicate three-p.r.o.nged hands.

The scaly hairless head beneath the Centaurian's white globe device bore a face that was blankly hideous. Two great lidless eyes, devoid of both pupils and whites, stared unblinkingly at Dixon like twin blobs of red-black jelly. A toothless loose-lipped mouth slavered beneath.

Dixon averted his gaze from the horror of that fearful alien face, and looked anxiously around for Ruth. He saw her almost at once, over at his right. She was tethered by a light metallic rope that ran from her waist to one of the metal beams supporting the great s.h.i.+mmering ball of opalescent fire which formed the central control of the hybrids.

One of the white globe devices had been placed upon Ruth's head and she was apparently unhurt, for she pluckily flashed a rea.s.suring smile at Dixon.

Directly in front of Dixon and some forty yards away there was a large pen-like enclosure, with vari-colored shafts of radiance from banks of projectors constantly sweeping through it. Dixon drew in his breath sharply as he saw the frightful life lying dormant in that pen. It was a solid ma.s.s of hybrids--great loathesome figures fas.h.i.+oned from a score of different worms, insects, and spiders. The globes upon the gruesome mammalian half-heads were still dark and unfired with opalescence.

The invaders had apparently raided most of the surrounding country in obtaining those grafted half-heads. Near where Dixon stood there was a tragic little pile of articles taken from the Centaurians' victims--prospectors' picks, shovels, axes, and other tools.

Over to the left of the dormant hybrids stood the second Alpha Centaurian, curiously examining Dixon's projectile. The creature apparently suspected the deadly nature of the gleaming cylinder for it soon laid it carefully down and packed cus.h.i.+ons of soft fabric around it to s.h.i.+eld it from any possible shock.

Then at an unspoken command from the first Centaurian the great hybrid whirled Dixon around to face a small enclosure just behind him in which were located banks of control panels and other apparatus. One of the pieces of mechanism, with a regularly s.p.a.ced stream of sparks snapping between two terminals, was apparently a radio receiver automatically recording the broadcast from the s.p.a.ce s.h.i.+p. Dixon was unable to even guess the nature of the remaining apparatus.

"Bruce, be careful!" Ruth called in despairing warning. "He is going to put the thought-reading machine on your brain. Then he'll learn what the projectile is for, and everything will be lost!"

Dixon's mind raced with lightning speed in the face of this new danger. He stealthily slipped a hand over the revolver in his pocket. There was one vulnerable spot in the great hybrid holding him, and that was the opalescent globe on the creature's head. If he could only smash that globe with one well-directed shot, he might be able to elude the Centaurians for the precious minute necessary to send the projectile on its deadly journey.