"Our life-line is narrowing, the earth is dying," the Master had explained. "That one-in-a-million chance of opportune conditions in which life may exist is vanishing. I doubt if the circumstances can be duplicated in the entire universe. But someday, by the very laws which govern chance, they must return again. It is not within the powers of man to bridge the gap of space and time, but you, Tau, the robot, swinging in the non-conducting realms of the vacuum of space, will be next to eternal." Tau had learned the secrets of extracting radiant energy from the atom, had become adept in applying the forces to the mechanisms that propelled the space-ship and supplied motivation for his own metal body. Many other secrets the Master had taught him in the laboratories, and he had come to know the uses of the scientific paraphernalia that was sealed in the inner heart of the space-craft. When the occasion came for Tau to use the equipment, Kendall Smith had said, he would understand the true nature constituting life. * * * * * The binary descended, and night fell. Glittering shards of the stars pierced the black firmament. Night creatures let out occasional shrieks and snarls. Once a six-legged catlike creature, half as tall as the metal man, was attracted by Tau's movements, and sprang upon him. Tau's responses were mechanical, and he knew no such thing as fear. He simply ripped the creature apart with the tremendous strength that surged in his metal arms. [Illustration: _Tau tore him to pieces._] Later that night he returned to the space-ship. As he approached the gleaming ovoid a circular door opened. Crossing its threshold, he passed into the interior, distorted by intricate mechanisms, and the aperture closed behind him. Slowly Tau walked to the center of the room, his body reflected in gleaming surfaces of berylite stanchions and sheathings. In the center of the whorled contrivances a row of ingenious troughs lay exposed. Each of these troughs was centered by a molding that had the perfect outline of a man, empty in the crystalline interior. All that night iridescent gleamings crawled along the monstrous glassite tubes, illuminating the busy robot with an eerie splendor. Miniature lightning shot and sparkled from insulated spheres high in the nose of the craft. Pulsating, sluggish liquids gave off radiant colors and seeped through tortuous channels along the tubes of glassite. The central troughs became opaque, and formed a webwork now into which the throbbing aqueous masses were assembling. A chill current of the outer atmosphere was forced by rotating blades along a channel that whirled in a maelstrom around the central apparatus. Tau worked swiftly, but days fled by as he watched the quiescent gauges and indicators, lengthened into months. Blinding storms raged unheeded on the exterior of the ovoid craft. Winter came and fled.