While driving through the New Mexico Desert during a rainy night, the college students Jim Halsey and his girlfriend Grace Andrews give a ride to the hitchhiker John Ryder. While in their car, the stranger proves to be a psychopath threatening the young couple with a knife, but Jim succeeds to throw him out of the car on the road. On the next morning, the young couple sees John in another car.

Upon arrival at the space station orbiting an ocean world called Solaris a psychologist discovers that the commander of an expedition to the planet has died mysteriously. Other strange events soon start happening as well, such as the appearance of old acquaintances of the crew, including some who are dead.