Sam Hervey moved swiftly. His lean wiry body twisted on the narrow bunk, the harness was thrown off--how had he gotten free so quickly?--and he was away, sobbing through his teeth, clawing at the bigger man. Joe Berne gasped in shock, falling back from the fury of the sudden assault. A hard fist crashed into his belly, and he cursed and swung the wrench. He cut air, and Hervey was scrambling away from him. The cabin door was jerked open, and in the dim tunnel light Berne saw his quarry plunging away, a shocked white face staring back over his shoulder. Cursing, Berne hurled the wrench. It was futile, of course. It drifted slowly away from his hand and crashed against the slammed steel door. Berne was trembling with rage; waves of sick nausea gripped him. His dismal failure writhed in his stomach, and he cursed again as he groped from the cabin. Hervey had turned off the tunnel light; in the darkness ahead of him, Berne heard Hervey scrambling along the handrails, and then a clatter as something fell. He plunged toward the sound, taking great leaps, using the power of his legs against the floor to hurl himself forward. He did not see the trap that Hervey had laid, the tangle of armored cable that Hervey had ripped from a locker and hurled into the narrow tunnel behind him. Berne smashed the cable, screaming obscenities at Hervey, and fought to free himself from the twisted mass. Hervey had bought time with the cabin door slammed in Berne's face, with the cable hurled from the locker into the tunnel. As Berne freed himself and leaped forward again, he heard the _woosh_ of escaping air as the inner air lock door was opened. Then the clang of the lock door echoed through the ship. Hervey was safe, for awhile. But he couldn't go far. Sobbing, mouthing curses, sick with anger, Berne struggled into space garb and opened the gunrack beside the lock. He saw with satisfaction that the fleeing Hervey had not waited to arm himself. Berne plunged through the lock. * * * * * The great banded face of mighty Jupiter seemed to fill the whole sky, lowering down on the jagged black waste of the asteroid. Five hundred yards from the ship the gray metal dome of Astarea Station huddled forlornly at the base of the soaring beacon tower. In the cold half-light, Berne saw the bulky space-suited figure of Sam Hervey running toward the station. Berne kneeled at the top of the ladder, took careful aim, and squeezed the switch of the heavy rifle. The rocket flame lanced out. Just behind the fleeing figure, and to the side, the rocket mushroomed in a brief blinding flare. Berne could see the glint of the face-plate as Hervey turned his head. He fired again, and cursed the weak light as he overshot. The running figure wavered, looked back, started again toward the safety of the station air lock--toward the radio that could call Mars Base, that could tell the story of murder....