spiders! How many men had died trying to explore it! And who knew it better than Penrun himself, the only one who had ever escaped from that hellish cavern of the Living Dead? Old Halkon had hidden his treasure well indeed.

Penrun had never found the Caves. Legend described them as the one safe place on the satellite where a man might live without danger of being attacked by the spiders because the Caves were too cold for them.

Penrun doubted if there was any place that would be safe from the monstrous insects.

At any rate old Halkon had hidden his treasure there, and that part of the map that Penrun had thought was a lake was apparently the main cavern, and the canals, side passages. Old Halkon believed that he had hidden his treasure well, but he could not foresee just how well. Two thirds of the map, showing the location of the entrance to the Caves, had been taken by the murderer of the Martian, Lozzo. The remaining third, which showed the location of the treasure inside the Caves, was in Penrun's possession.

The murderer could find the Caves, but not the treasure inside; and Penrun could find the treasure inside, but not the Caves.

Penrun folded up the crumpled bit of paper and placed it carefully in his shoe. Unless his guess was wrong, another attempt to get it would be made shortly. Undoubtedly the girl had by now reported her failure to the rest of the gang.

The inquest was brief. The white-sheeted body of the Martian lay on the table where he had been slain. The captain of the liner called Penrun as the chief witness. He told a straightforward story of a chance acquaintance with Lozzo who, he said, seemed to be afraid of something. He had declared, so Penrun testified, that he was being hounded for a map of some kind and he wanted Penrun to see it. Then the murder had been committed, the map was stolen, and the murderer had fled. That was all, Penrun concluded, he knew about the matter.

Other passengers corroborated his story and he was dismissed.

Throughout the inquest Penrun studied the crowd of passengers that jammed the buffet, hoping he might catch a glimpse of the slender, dark-eyed girl who had tried to rob him. She was nowhere to be seen. He thought of telling the captain about her, but decided not to. She might make another attempt to get the map, and thereby give him the opportunity of rounding up the whole gang, or at least of learning who they were. He told himself grimly that if he could lay hold of her again, she would not escape so easily.

If Penrun didn't realize before that he was a marked man, it was impressed on him more forcefully three hours later on the lower deck when two men attacked him in the darkened passage near the stern. There was no time for pistols. A series of hurried fist-blows. He slugged his way free and fled to the safety of his stateroom.

Once there he locked the door and sat down to consider his position. It was obvious now that he would be followed to the outposts of space, if necessary, in an attempt to get the map from him.

After half an hour's hard thinking he tossed away his fourth cigarette, loosened the pistol in his armpit holster, and slipped out of the room. He went to the captain.

"You think, then, that your life is in danger because you happened to be talking to that old Martian when he was murdered?" asked the captain, when Penrun had finished.

"No question about it," declared Penrun. "Two attempts have been made already."

"Hmm," said the captain, frowning. "A most remarkably strange business. I've never had anything like it aboard my ship in the twenty years I've been traveling the Void."

"I can pay for the space-sphere," urged Penrun. "My certificate of credit will take care of it with funds to spare. All you have to do is to let me cast off at once. If any questions are asked, you can say it was my wish."

"Hmm! Really, Mr. Penrun, this is a most unusual request. I'm not inclined—"

He stared at the communication board. The meteor warning dial was fluctuating violently, showing the presence of a rapidly approaching body—a meteor, or perhaps a flight of them. Gongs throughout the liner automatically began to sound a warning for the passengers to get into their space suits. The captain sat as though petrified.

Penrun sprang to the small visi-screen beside the board and snapped on the current. Swiftly he revolved the periscope aerial. There appeared on the screen the hull of a long, rakish, cigar-shaped craft which was overhauling the liner. The stranger was painted dead black and displayed no emblem.

"There's your meteor, Skipper," he remarked ironically. "And I am the attraction that is drawing it to your ship for another murder. Do I get the space-sphere?"

The captain sprang to his feet. "You get it, Penrun. You'll have to hurry. I want no more murders aboard my ship. Here, down this private stairs to the sphere air-lock. I'll make arrangements by phone. Once you are free of the liner I'll slow down so that the black ship will have to slow down, too. That will give you a chance to pull away and get a good start on them."

Five minutes later Penrun's newly acquired craft was sliding out of its air-lock in the belly of the monstrous liner. He pulled away and glanced back.

The liner was already slowing down. The black pursuing craft was hidden by its vast, curving bulk. Penrun crowded on speed as swiftly as he dared. By the time the strange craft had made contact with the Western Star his little sphere had dwindled to a mere point of light in the black depths of space and vanished.

Penrun leaned over his charts grimly, as he set a new course for the sphere to follow. He, too, could play at this game. He'd carry the battle to the enemy's gate. Out to Titan he'd go and match his familiarity with the little planet against the superior numbers of his enemies.

Ten days later, Earth time, he was circling Titan, while he searched the grim, forbidden terrain beneath. After days of studying and speculation he had decided that the Caves must be situated in the Inferno Range, a place so particularly vicious that no man, so far as was known, had ever explored it. During the day the heat would boil eggs, and at night the sub-zero cold cracked great scales off the granite boulders. And here, too, lay the Trap-Door City of the monster spiders!

The grim, fantastic range soon appeared over the horizon, stabbing its saw-tooth peaks far into the sky. Dawn was still lighting the world, and a great snow-storm, a howling, furious blizzard, concealed the lower slopes of the mountains. Penrun knew that presently the driving snow-flakes would change to rain-drops, and the shrieking, moaning voice of the gale would give way to the crashing, rolling thunder of the tempest. As the day advanced the storm would die abruptly and the clouds vanish under the deadly heat.

Then the Trap-Door City, which covered the slopes above the plateau at the three-thousand-foot level like a checker-board of shimmering, silken circles, would spring to febrile life as the spider monsters went streaking and leaping across the barren, distorted granite on the day's business, the hunt for food in the lowlands, and the opening of the trap-doors to gather in the heat of the day in the silken tunnel homes set in the gorges and among the boulders. At sunset the doors would all be closed, for then the rain and the electrical storm would return, and at night the blizzard. The storm-and-heat cycle was the deadly weather routine of the Infernos.

Penrun steered for a tall, cloven peak that towered high above the Trap-Door City. In its thin air and continuous cold he would be comparatively safe from marauding spider scouts, and from the peak he could watch not only the city of the monsters but the better part of the Inferno Range as well.

He was convinced that before long the