Before him stood a case, transparent, hard and crystal-like, as long as a man's body and half as deep, standing level on short metal legs. What it contained was the most jealously guarded, the most precious of all Dr. Ku Sui's works, the very consummation of his mighty genius, his treasure-house of wisdom as profound as man then could know. And more: it held the consummation of all that was so coldly unhuman in the Eurasian. For there, in that case, he had bound to his will the brains of five of Earth's greatest scientists, and kept them alive, with their whole matured store of knowledge subservient to his need, although their bodies were long since dead and decayed. For some time the adventurer stood lost in a mood of thoughts and emotions rare to him--until he was startled back into reality by a heavy, clumping noise coming down the corridor through which he had entered. His gun-hand flickered to readiness, but it was only Friday, coming as he had been ordered. Carse greeted the Negro with a nod, and said briefly: "There's a panel in this room--over there somewhere--you remember--the place through which Ku Sui escaped when we were here before. It's an unknown quantity, so I want you to stand watch by it. Open your face-plate wide, and warn me at the slightest sound or sight of possible danger." The Negro nodded and moved as silently as was possible in his space-suit to obey. And Carse turned again to the thing to which he had made a promise. * * * * * The icy-glittering case was full of a colorless liquid in which were grouped at the bottom, several delicate, colored instruments, all interconnected by a maze of countless spidery silver wires. Sheathes of other wires ran up from the lower devices to the case's main content--five grayish, convoluted mounds that lay in shallow pans--five brutally naked things that were the brains of scientists once honored and eminent on Earth. Their bodies has long since been cast aside as useless to the ends of Ku Sui, but the priceless brains had been condemned to live on in an unlit, unseeing deathless existence: machines serving the man who had trapped them into life in death. Alive--and with stray memories, which Ku Sui could not banish entirely, of Earth, of love, of the work and the respect that had once been theirs. Alive--with an unnatural and horrible life, without sensation, without hope. Alive--and made to aid with their knowledge the man who had brought them into slavery unspeakable....