Thirty miles they went, from the limits of Louisville. They got to a farmhouse that was a tumbledown ruin. Behind it there was a barn, in even worse shape.

The man turned into the drive of the vacant place. He got out of the car. Keane followed. The man went into the barn.

There he walked directly to a mound of hay. There was a bit of wood at the edge of the mound. The man grasped this and pulled it. The hay mound turned, as though resting on a turntable. A square hole was revealed in the barn floor with steps leading down.

"Where does this go?" demanded Keane.

"It strikes a short tunnel that leads into a cave. I don't know where the cave ends. I think it is a far part of the Mammouth Cave system. Anyhow, I know it goes for a long, long way. And somewhere back in it, my master, Doctor Satan, stays.

Keane took a deep breath. He had trailed Satan to many different lairs, but none of them promised to be as appropriate as this. It was fitting that a man masquerading as Lucifer should have his haunt in the bowels of the earth - near h.e.l.l, if there were such a place.

The man who had driven him walked down the steps and touched a projecting stone. The hay mound above slid into place, leaving them in thick darkness.

"Now?" said Keane.

The man pointed. Keane felt his arm go up, looked in the direction of its extended finger. Far ahead, he saw a pin-p.r.i.c.k of light.

He turned to the man.

"You will sleep," he said quietly, his hand on the man's arm.

"I will sleep," was the somnolent answer.

Keane felt the man lowering himself to the rock floor of the crude tunnel they were in. He felt him lie down, heard no further movement. Alone, he started toward the pin-p.r.i.c.k of light far in the distance - and toward whatever weird place Doctor Satan had fixed down here as his lair.

"A lair near h.e.l.l," Keane muttered as he felt his way along toward the distant light. "Please G.o.d I can send you to h.e.l.l tonight."

4. h.e.l.l's Anteroom The tunnel down which Keane walked grew constantly lighter. As it lightened, it turned faint rose-colored from the oddity of the light ahead. And now Keane heard a faint roaring from that same light.

He got nearer, and saw that the light across the tunnel ahead of him was not constant; it flickered and twisted, like a great yellow serpent.

Then he saw the nature of it.

Up from the rock floor roared a column of flame at least two yards across. It disappeared through an orifice in the rock ceiling, stretching from floor to top like a solid column, save it twisted and writhed constantly like the fiery serpent it resembled.

Keane stopped. The rock beneath him was trembling with the fury of the pillar of fire. The heat blasted at his face twenty feet away. It was a door to what lay beyond the tunnel more forbidding than any portal of steel.

"Natural gas," he muttered.

But a guess as to the nature of the column did not help him pa.s.s it. That stopped him, for the moment. But, he reflected, there must be a way to tame the pillar. People pa.s.sed along there. They couldn't do that if the flame persisted constantly.

He thought of going back and getting as guide the man he had left in hypnotic slumber at the tunnel mouth. But that was not necessary. Even as he thought that, he heard the roar of the pillar diminish a little, felt the rock shake less violently under his feet.

The fiery column was dying down. It burned less brightly as he watched it. It sank till he could see the leaping crest of it top under the low ceiling.

And over that crest he saw a man's head, on the other side. It was a head to induce nightmares. Like a naked skull it was, with unbelievably little flesh to clothe it. In deep eye-sockets, drugged eyes peered forth.

The flame" died down still lower. Keane saw the man's body, as skeletal as the head. And as the emaciated body was more and more revealed by the subsiding of the flames, Keane shrank back into a niche in the wall to be out of sight. He opened the bundle he had brought with him.

From the bundle he took the costume he had worn in the hospital to restore Jane Ivor's sanity; red cloak, red mask, red skull-cap, red gloves - point for point a costume matching Doctor Satan's own as Keane remembered it from former encounters.

He donned cloak and gloves, started to put on the mask.

But by now the pillar of fire had sunk below the floor level, down into the hole from which it sprang. It left only a ragged orifice like the mouth of a well in the rock floor. The opening was only about six feet across. Keane, looking around the corner of his small alcove, saw the emaciated man with the drugged, staring eyes, leap this hole and start walking down the tunnel toward where he hid.

There was no time to don the mask and skull-cap. The man was abreast of the niche before Keane could get them on. He stared at Keane in the lessened light of the lowered flame. His mouth opened for a shout.

Keane felled him with a blow to the jaw. There was neither time nor need for subtler measures. He caught the falling, thin body and lowered it to the floor just out of the way of the tunnel itself. Then he put on the mask and the skull-cap and with the two projecting k.n.o.bs mocking imitation of Satan's horns.

Tall and spare, with the red robe arrogantly draped over his broad shoulders, he stalked toward the hole into which the flame had sunk - an exact replica of Doctor Satan himself. Already the roar of the fiery pillar was increasing again, and he saw the tip of the flames as it started to rise once more to bar the tunnel.

He leaped the two-yard opening. Heat seared him for an instant, threatened to set fire to his robes even in the half-second of his jump. But he got to the other side ....

Behind him the fire column rose to the ceiling in its full strength. His way back was cut off. Before him - - - Keane looked, and gasped aloud.

He was in a great, low cave, extending before him farther than the eyes could penetrate. Stalagmites, like withered, warped bodies, thrust up from the floor. Stalact.i.tes dripped from the low ceiling. Among the stalagmites half a dozen figures moved; figures no less warped and distorted than the limestone pillars around them.

Keane's eyes narrowed as he looked at them. He had guessed that Doctor Satan had more accomplices here than he normally used in his devilish business; the layout of the place had indicated that. But he had not reckoned on so many, and he had not dwelt on the possible caliber of the accomplices.

Doctor Satan must have scoured the underworld to get these men who were smoothing the floor of the cave, storing supplies, In general working to make of it a permanent and sumptuous base for their diabolical master. Keane had never seen such seamed, degenerate, evil countenances! Why, with the red light from the flame pillar flickering over the weird cavern, and over their twisted bodies, they looked like demons in a real h.e.l.l!

Now two of them glanced toward him, and shouted aloud. They straightened, and the others straightened with them. At attention, like ghouls parading before the Devil himself, they waited the orders and coming of the one dressed in Lucifer's red robe.

Arrogantly, imitating Doctor Satan's stride, Keane went toward then. And he saw again, in every eye, the glazed look he had seen in the eyes of the policeman and the man who looked like a walking skeleton. Doctor Satan was taking no chances of disaffection or insubordination among the rabble he had chosen to set his evil underground house in order. He had made each of them a slave to his hypnotic will.

"Somewhere back in ... the cave system... my master, Doctor Satan, stays."

So had had the man Keane had come to the caves with. Keane, not glancing at the murderous-looking men who stood at attention, stalked past them and toward the far end of the big cave. But as he went, his mind wrestled with a thought as breathtaking as it was monstrous.

So much like a real h.e.l.l, this place looked! So much like actual, inhuman demons appeared the dregs of criminal humanity working in it!

Doctor Satan masqueraded as Satan. Yes, but was it all masquerade? Was it not conceivable that - Lucifer being only a personification and t.i.tle for the evil pa.s.sions of men? Doctor Satan was actually Lucifer, or as near to it as a being could ever be?

Keane shrugged the thought aside. True or fanciful, it was beside the point; the point being the destruction of the master criminal who had given rise to it.

He got to the end of the big cave at last, and squeezed through a rock opening barely large enough to admit his lean but powerful body, into another smaller cave. And with his entrance into this he instantly leaped sideways and behind a big stalagmite. For in this second cave was everything he had come here to find.

Tensely, cautiously, he peered around the concealing rock cone....

To one side of the cave, which was roughly circular and about fifty feet in diameter, was a legless giant who supported his torso on muscular arms as big as most men's thighs. The man's stupid, cruel eyes blinked toward the center of the cave. This was Bostiff, Satan's main lieutenant in crime since Keane had blasted his other lieutenant, Girse, out of existence. He was looking at two figures in the center of the place.

One of these was a boy of nineteen or so, dressed in expensive clothes which were now wrinkled and stained. The boy's face expressed terror beyond that tolerable to sanity. His wild eyes glared at the figure that faced him with the fascination in them expressed in the eyes of a small animal hypnotized by a snake.

And this other figure was that of Doctor Satan himself.

Tall and arrogant it towered over the boy, who was Harold Ivor, brother of the girl who had been left, a maniac, on the main street of Louisville. It was garbed in red from head to foot and, point for point, was as like the red-clad figure of Keane, concealed behind the stalagmite, as a reflection of that figure in a mirror.

Only in one detail did the two identical figures differ. The eyes peering through the holes in the mask covering Keane's face were steel-gray. The eyes of the figure towering over the boy were black, lurid, infernal.

"Who am I?" Doctor Satan rasped to the boy.

Harold Ivor, panting, glaring helplessly into the arrogant black eyes, replied: "You are Lucifer.

"You truly believe that?"

"I truly believe that."

Keane, behind his concealing pillar, felt glacial rage flood through him. He had got here just in time to witness Doctor Satan's method of driving his victims mad. He had turned Jane Ivor into a maniac. Now he was doing the same to Harold Ivor. Then the boy would be released in the town as Jane had been - a second horrible object-lesson as to what happened to the children of the rich if their parents did not pay to prevent it.

"Whom do you serve?" rasped Doctor Satan to the lad.

"I serve you, Satanic Majesty. And I will kill your enemies."

There was a silence, while the black eyes of the masked figure stared into the glazed, mad eyes of the boy.

"Bostiff," Doctor Satan said.

The legless giant swung his body toward his master, using the calloused backs of his hands as feet.

"Take him to his prison. Another session like this and he will be ready for release."

"Yes, master."

Bostiff seized the boy's hand, propelled him toward an opening in the cave. He dragged himself after. The two went through the opening.

The red-robed figure in the center of the cave was alone.

The red-robed figure behind the stalagmite near the door, drew up to its full height, then stepped out of its place of concealment.

Doctor Satan had been staring at the opening through which Bostiff had gone with Harold Ivor. How he whirled like an uncoiling spring, and stared at Keane. And in his black eyes was a sudden madness of surprise, hate and rage.

Keane drew near him. He stood before Satan, and the result was fantastic.

Two Satans stood there; two Lucifers, clad in red, red-masked, with Luciferian horns. The Devil and his double! Crimson twins, with death in the eyes of each.

Then Doctor Satan stepped toward Keane with right hand clenched.

"Keane!" he grated. "Again! At every turn I find you - squarely in my path! But this time that path shall lead ahead without obstacles, to limitless power."

"No, said Keane softly, "this time the path shall be blocked if my dead body must be used to block it!"

5. The Scarlet Twain Doctor Satan took a step nearer the figure so closely resembling his own. His black eyes played sardonically over Keane's red cloak.

"So," he grated, "in order to get past my men you imitated my trappings. You made a mockery of the masquerade it amuses me to wear."

Keane shrugged.

"It seemed the easiest way. I was sure you had many serving you here. I didn't want to kill them. It seemed easier to get past them by trickery."

"And having pa.s.sed them," said Doctor Satan, "what then?"

Keane's mask stirred to the deep breath he drew.

"This," he said softly. "A thing I think even you are unfamiliar with, Doctor Satan. You will learn of it shortly. And it will be the last thing you ever will learn about!"

His hand went under the red cloak. It came out of his pocket with the weapon he had carried from the hotel - his one weapon, on which he was staking everything.

He opened his fingers and let Doctor Satan see the egg-shaped thing lying on his palm. It was smooth, perhaps two and a half inches long by two inches through. It seemed to be made of gray vitrum.

"Long ago," Keane said, "there were inquiring minds more versed in their own science than our present-day scientists, with their research laboratories and fine equipment, are in theirs. That was the science of Black Art. This is one of the results. I found it in the ruins of a Druid monastery in England."

Doctor Satan stared at the thing in Keane's hand. And as he stared, his black eyes lost their arrogance and became filled with the shadow of dawning fear.

"Where did you...get your knowledge of what this is?" he breathed, voice thick. "Why, it is...it is the-"

He stopped, and a silence like that of the grave held the cavern.

"It is the Blue Death of Saint Sartius," said Keane. "It was first used in Rome. Then its secret was forgotten till the black ages, when a Druid monk rediscovered it. I have read records of the death of everyone in a certain town in England. The records stated that an odd sort of plague was responsible, but intimated that death was caused by some of these."

His fingers clenched over the vitreous sh.e.l.l.

"Sarlfolk," whispered Doctor Satan hoa.r.s.ely. In his black eyes was a fear he had never shown before. "I have read the records, too. The town of Sarlfolk - depopulated overnight and never occupied again - But that can't be the Blue Death you hold In your hand! Its secret was again lost when England was still a wilderness with men like animals populating it."

Keane's masked lips moved in a bleak smile. He raised the egg-shaped thing in his hand.

"You'll find out," he said.

And he threw the thing with all his force at the feet of Doctor Satan!

Satan screamed. It was the first scream of terror that had ever come from the shielded, perpetually hidden lips. He leaped back from the object that had burst like a tiny bomb save that no explosion accompanied it. But quick as he was, he had acted too late.

Keane had thrown it so that it burst to pieces between him and the only two openings from the cave - the one into which Bostiff had taken Harold Ivor, and the one through which Keane had come. And with the instant of its bursting, the vitreous egg had emitted that which rose as a barrier to those exits.

From the broken sh.e.l.l a bluish, heavy mist rose rapidly and moved toward Satan as though acting with a will and intelligence of its own.