Another scream tore from Satan's shielded lips. He was probably the only man on earth, aside from Keane, versed enough in the occult to know what terror it was that crawled toward him. But he knew well enough!

The bluish mist spread with the rapidity of flame devouring straw. It poured from the broken sh.e.l.l like a rolling wall. And it formed in a half-circle around Satan, forcing him back toward the rock wall of the cavern.

In Keane's eyes was the glitter of triumph long delayed.

"You'll know now some of the anguish you've caused others," he said savagely. "You'll know some of the torment endured by the men you've killed - some of the mental torture being undergone at this moment by the parents of the children you threatened. I could feel sorry for anyone facing the Blue Death of Saint Sartius, but not for you."

There was a shuffling sound at the entrance through which Bostiff and Harold Ivor had gone. Bostiff had reappeared. He swayed in the doorway, eyes glinting with brute surprise as he saw two red-robed figures where only one had been before, and with fear as he saw without understanding the blue fog that was rolling toward the one he recognized instinctively as his master.

"To me!" Doctor Satan screamed. "Bostiff---"

The legless giant turned, snarling, toward Keane. Then he turned back obediently toward Satan and began hitching his body toward the blue fog on his hands.

"No!" breathed Keane in something like horror as the legless man hitched forward. But he did not utter the word aloud. Bostiff was as evil as his master, limited only by his own thick-wittedness. He deserved death as well as Satan.

Bostiff reached the edge of the blue fog, paused, then groped a little into it.

A scream suddenly came from his distorted lips. And the fog, touching him, underwent an instant change.

From being a sort of mist, it became a clinging, viscous shroud. Bostiff began wrenching and tearing at it as it poured itself swiftly over and around him. The viscous shroud grew more opaque, palpably harder. It was as though the legless man were suddenly encased in frosted blue gla.s.s.

His hoa.r.s.e shouts died in volume. Through the blue opacity his staring eyes, like the eyes of a man caught under ice and swimming desperately under water to find the hole he fell through, peered out.

"Master! Save me.'"

The shout could barely be heard. And in any event Doctor Satan wasn't listening. Nor could he have done anything - if he had.

The blue mist had reached him now. It circled him closer as he crouched against the rock wall as though trying to force his body into it. It touched his face....

Doctor Satan's hands were up, fingers extended in a cabalistic sign. His lips were moving the red mask over his face as they chanted a ritual not heard by human ears for fifty generations.

And as he watched, perspiration studded Keane's face under his mask. The blue fog was slowing a little. Was it possible that Satan could evade this death?

But the fog, halting for a moment with the cabalistic signs and the incantation, surged forward again. Incredibly, the mist-like stuff grew what seemed to be horrible tentacles. The shreds of them wrapped around Satan's red-sheathed arms and dragged them down.

A few yards away, Bostiff was now only a coc.o.o.n of a thing lying moveless on the floor. Even his ghastly, staring eyes could not now be seen. The fog portion that had wrapped around him had hardened like the vitrum of which the sh.e.l.l of the egglike object containing it had been made. Keane repressed a little shudder. Such a fearful death!...

Doctor Satan was down now. Over him, as it had over the legless man, the blue mist was becoming a viscous, sticky sheath. But Satan had stopped screaming. Keane saw his black eyes glisten through the mask with fearful intensity of thought.

Next moment Keane found out what the thought had been directed at.

A man stepped through the narrow portal into the first cave off the flame. Another man followed, and another. Six men lined before the opening and began to advance on Keane. Slaves of Satan's hypnotic will, they had been called silently, from this distance.

Keane exclaimed aloud, though not in fear of his own safety; the summoning of these comparatively stupid mortals was a futile last gesture, as Satan must have known in his extremity. The thought that wrenched the cry from Keane's lips was the fear that by sheer numbers the men might defeat the death he had brought here for the red-robed fiend he had struggled against so long.

The Blue Death could surround and kill only a limited number of bodies! True enough, the ancient records hinted that the Blue Death had killed all the inhabitants of the old town of Sarlfolk. But if that were so, a great deal more of it must have been released than had been carried here in Keane's egg!

The deadly blue mist would attack every moving thing within range save the being that directed it! But it took a definite amount of it to kill. It now surrounded two forms. If it divided to surround six more - would there be enough to kill them all?

For once in his life, Keane wished he had a gun. In his deadly resolve to overcome Doctor Satan at all costs, he would have shot these men, because their dead bodies would not have drawn aside any of the fatal mist. But he had no gun, and he could not attack six men bare-handed. Biting his lips, he could only watch what took place.

Meanwhile the six men, hypnotized by Doctor Satan and acting blindly according to his will, sprang at Keane. With an athlete's quickness, he dodged their concerted rush. Two of them plunged into the Blue Death, already rolling toward them. One, laying hands for an instant on Keane, he flung into the ominous fog. The other three started to attack a second time, and stopped like ice-sheathed statues as the Blue Death reached them.

Keane's breath came between his clenched teeth in a ragged hiss. Eight bodies were cased in the viscous blue stuff which the mist became when it touched flesh! They lay like coc.o.o.ns on the rock floor, some motionless, some feebly writhing, but all things of horror and despair.

Keane went to the form which still showed a little reddish through the blue crust over it - the form of Doctor Satan.

Terror-filled, dulling bleak eyes stared at him through the fearful sheath. Red-gloved hands raised a little, crackling the blue stuff that cased them, in a final gesture of malediction. Then they fell and the black eyes closed.

"Thank G.o.d!" breathed Keane, voice harsh and cracked.

The fight was over. He was sure. To make doubly sure, he would have liked to strangle that stark form; to have clubbed its head in. But he dared not touch the blue sh.e.l.l. That would have meant death for him, though he himself had released it.

He went to the opening through which he had seen Harold Ivor taken. The boy was beyond, in a small cave like a prison room. He was cowering against the wall, and he shrieked and threw up his hands as Keane entered in his red masquerade.

Keane dragged off his mask, and threw back his red hood. The boy stared as Jane Ivor had stared.

"You're-you're a man?" he sobbed. "You're not---"

Keane smiled, and in that smile was a gentleness that erased the fear from the boy's face.

"I am not Satan," he said. "There is no Satan-at least, none to frighten you any more.

As Jane Ivor had done, her brother, Harold, swayed in the beginning of a fainting fit from shock. But he had not been as far driven in madness, yet, as his sister had been. He reeled from the shock, but he did not lapse into unconsciousness. And after a moment he came to Keane, trembling hand outstretched.

Keane grasped it.

"Come," he said. "We'll leave here. We'll leave this h.e.l.l, and the demons in it, and its master - all dead---"

But then, as he got to the door, a hoa.r.s.e shout was wrung from his lips. He leaped to the spot where Doctor Satan had been lying, eyes wide with a shock of astonishment that almost unnerved him.

The spot where Doctor Satan had lain was empty. His blue-sheathed form was no longer there. And over the bodies of the seven who had served him, the blue casing was a little thicker.

"d.a.m.n him," raged Keane, trembling fists raised. "d.a.m.n him!!"

Satan had gathered the remnants of that icy, terrific will of his while Keane was away with the boy, and had, out of his own fragmentary knowledge of Saint Sartius' Blue Death, contrived somehow to divert its hardening sh.e.l.l from his own body and onto the others that lay near by.

That was obviously what had happened. But, sick with defeat when victory had been tasted, Keane refused entirely to believe it till he got to the anteroom cavern with Harold Ivor.

The flaming pillar was down. Someone had just pa.s.sed this way and had hurdled the well-mouth opening from which the fire hissed.

Had that someone hurdled it feebly, barely dragging his body up the opposite edge? Keane thought so. For on the far edge of the small abyss was a single, torn, red glove.

But, feebly or not, Doctor Satan had escaped from the caves. Again he had cheated with death to which Keane had driven him closer than he had ever been before in his satanic existence.

The flame pillar was already rising again.

"You must Jump that hole," Keane said to the boy.

He set the example. The youth followed. Clinging to Keane's hand, Harold Ivor went with him down the outer tunnel.

The concealed trap-door above was open, as Satan had left it, too hard-pressed and weak to bother to shut it after him. Under the door the man Keane had hypnotized after his use as guide had been no longer needed, lay stretched on the floor. Eyes open and blank, he slept the sleep from which there is no awakening save by the action of the one who induces that sleep.

Keane started toward the man, then stopped. He was a human rat. The emanations from his hazed mind caught by Keane's superhuman psychic perception whispered that he was at least once a murder, perhaps twice or thrice.

Face bleak, Keane went on past him with the shuddering boy. He left the man sleeping there...

Outside, in the driveway of the abandoned farm, the blue sedan was gone. Keane bit his lips as he visioned the swaying, raging figure in red at its wheel, speeding off somewhere into the night - to strike at humanity again when he had recovered.

Somberly, with his shoulders drooping, Keane started toward town with the boy. He had stopped the reign of terror in Louisville - but his real work was not yet done.

BEYOND DEATH'S GATEWAY.

The sea was as calm as a pond. Over it the great ship floated like a ghost vessel, dipping a little to long, slow swells but otherwise as motionless as a thing on a backdrop. The white moon poured down its peaceful flood, but somehow the peace was an eery thing and not rea.s.suring.

In a large cabin on deck A, two men sat behind a locked door and talked in whispers too low to be recorded if there were a dictograph receiver concealed anywhere. One of the two had the often-photographed face of .a.s.sistant Secretary of War Harley. The other was Jules Marxman, inventor and manufacturer.

Harley, a slim, precise, elderly man who looked more like a high school principle than an important Government official, shook his head a little.

"Then, as the invention now stands, it is useless," he summed up.

Marxman, the inventor, nodded his bushy gray head. His heavy grizzled brows drew into a straight line.

"Useless," he conceded. "I have the formula for the poison gas completed. It is perfect - a gas so volatile that it spreads at a rate of a hundred feet a second in all directions, and wipes out all living things, including vegetable matter. But its very speed makes it impossible to use it as other war gases are used. It would wipe out the men releasing it as well as the enemy."

"Special masks to protect our own men?" suggested the a.s.sistant Secretary of War.

Marxman shook his head.

"I thought of that, of course. I worked along that angle for a long time. But no mask can be devised to protect a man from the gas. So the answer lies in another direction. That is, an antidote of some sort for it that will permit the men releasing it to feel no ill effects from it."

"That sounds difficult. Look here, couldn't the stuff be shot from guns to explode and radiate at a distance?"

"No. It is so highly explosive itself that no sh.e.l.l can be designed to keep it from exploding when the gun charge bursts, when its high volatility spreads it all around the gun. Again, our own men would die from it. No, the only answer is the antidote that will make the corps releasing it immune to its deadly effects."

Harley stroked his long, spare chin.

"You've worked along that line, Marxman?"

"Yes, I have been working on an antidote for eighteen months. The final solution is not yet worked out. But I'm getting close."

Marxman looked at the locked cabin door, and lowered his voice still more.

"I have an antidote at present that will counteract the effects of the gas. But its own effects are almost as serious: The man who takes it literally dies for a short s.p.a.ce of time. His heart and breathing stop. Blood circulation ceases. He's a dead man - for about twelve hours. Most curious."

"And, most unfortunate," Harley said dryly. "In twelve hours the enemy from beyond the radius of the spreading gas could gun and bomb the helpless crew out of existence. But tell me, how can men 'die' for twelve hours, with the blood stream stilled and liable to coagulate, and then come to life again? Or - do they?'

"Yes, they do, I don't yet know how. The blood should coagulate, but it doesn't. Perhaps some life force beyond power of detection still functions enough to keep the body in shape to be reanimated when the effect of the antidote wears off. Anyhow, that's what happens to a man who takes it in its present state. He literally dies for half a day, then comes slowly back to life again."

"Have you tried it on anyone?"

Marxman nodded. His face was a little paler than normal.

"What happens to the subject of experiment?"

Marxman looked at Harley for a moment before replying, "I tried it on a dock laborer, several times. He wasn't a clever or educated man. He didn't manage to express very well the things that happened to him. But as far as I could gather, he was in the land of the dead during the coma induced by the drug."

"Land of the dead.'" Harley exclaimed. Then he smiled."And where is that?"

"I don't know."

"What's it like?"

"I don't know that, either, my man hadn't the vocabulary to describe such things in the first place. In the second, he didn't want to talk! And, though he was fearless in a blunt, animal way, he refused to take the stuff more than twice."

"Probably it has some sort of hashish effect," said Harley shrugging. "Land of the dead! That's a little thick! But regardless of that angle of it - the poison gas invention is not yet ready to turn over to the war department. Is that it?"

"That's it," said Marxman. "The gas is perfected, but the antidote is not. And until it is, the whole thing remains only a novelty, a dream of empire that can't be crystalized till I have finished work."

Harley fingered his lean chin.

"Don't overlook the fact that, even as matters stand, you have a very valuable secret," he warned. "Any power on earth would pay millions for the uncompleted formulae, on the chance that they could work out the conclusion in their laboratory. You have the formulae written out?"

Marxman nodded.

"They're too complicated to carry in my head."

"You keep the papers in a safe place?"