The inner catapult door closed behind Kenneth Torrance, and he slid into his torpoon. Twelve feet long, and resembling in miniature a dirigible, was this weapon that made practical an underwater whaling craft. The tapered stern bore long directional rudders, which curved round the squat high-speed propeller: its smooth flanks of burnished steel were marked only by the lines of the entrance port, which the torpooner now drew tight and locked. Twin eyes of light-beam projectors were set in the bow, which was cut also by a vision-plate of fused quartz and the nitro-shell gun's tube, successor to the gun-cast harpoon. Ken lay full-length in the padded body compartment, his feet resting on the controlling bars of the directional planes, hands on the torpoon's engine levers. A harness was buckled all around him, to keep him in place. His gray eyes, level and sober, peered through the vision-plate at the outer catapult door. Suddenly a spot of red light glowed in it; the door quivered, swung out. A black tide swirled into the chamber. There came the hiss of released air-pressure, and the slim undersea steed rocketed out into the exterior gloom, her light-beams flashing on and propeller settling into a blur of speed as she was flung. * * * * * Ken turned on her full twenty-four knots, zoomed above the dark bulk of the slower mother ship, whose light-beams flashed across him for a second, and then straightened out in a long, slight-angled dive after the great black bodies ahead. Aware that some strange enemy was on their track, the killers had become panicky and were darting away at their full speed, which was only slightly under that of the torpoon's humming motors, and which at times even surpassed it. Ken saw that it looked like a long chase, and settled his lean body as comfortably as he could. His mind was not concentrated on the task ahead, for the first part was mere routine and he could follow his quarry almost mechanically. And so, as his steel shell drove through the ever-shadowed, icy sea, he began to think about the disappearance of Chan Beddoes, the _Narwhal's_ second torpooner. Dead, now Beddoes; it was a week since he had set out on the chase from which he had never returned. Ken could only conjecture as to what had stricken him down. There were countless possibilities: perhaps a blow from a dying killer whale's flukes bursting his torpoon's seams; perhaps a crash into underwater ice. Whatever it was, it had been sudden, for not even a faint radioed S.O.S. had trembled into the ear-phones of the _Narwhal's_ radio-man. For two days they had held hopes that the second torpooner still lived, as the sea-suit stored in each torp contained air-units sufficient for thirty-six hours. But a whole week's passing told them that that vast stretch of glacial sea was now Chan Beddoes' grave.