Having accidentally traveled through time, astronaut Joseph Reardon lands on Earth in the year 2148 A.D. to find desolation.
He meets Andro, a mutated but erudite survivor of a biological disaster brought on by an ambitious 20th century scientist named Bertram Cabot Jr. Cabot isolated and developed a viral symbiont from an interstellar microbe that physically altered the entire human race, precluding the ability to reproduce, and turned much of Earth's landscape into a barren wasteland.
But Reardon claims there is hope, and attempts to return to his own time, taking Andro with him as a warning of what the future holds and to prevent the disastrous outcome.
However, while making the return journey through the time rift, Reardon slowly dies and mysteriously vanishes.
The deformed Andro, now landed on Earth in the present, can project himself as a normal human using hypnotic suggestion, and uses this ability while searching for Cabot.