Abner Harris was sent to Earth on a mission of extreme urgency. The universe was in danger of enslavement by the Medlins, and the fight against them called for Harris to assume the disguise of a flesh-and-blood Earthman.
But he discovered...
Simeon Krug, un poderoso industrial que construyó su imperio con la creación y producción en serie de androides, está empleando todos sus recursos en erigir una gigantesca torre de cristal destinada a contestar un mensaje...