Simeon Krug's obsession is to see a tower built, on kilometre high, that will reach out to answer the voice from space. The Androids are his tools; superb, man-like creations of Man. The Androids take Krug for their God, and seek to become one with flesh-and-blood mankind through his wisdom. But Krug is not God - and it takes a God to control the terrible emotions Krug has stirred . . .