In the year 3978A.D. a spaceship with a crew of 4 crashes down on a distant planet. One of the crew members had died in space and the other 3 head out to explore the planet. They soon learn that the planet is much like their own. They then find the planet is inhabited by intelligent apes. One of the men is shot and killed and the others are taken to the apes' city. There, one undergoes brain surgery and is put into a state of living death. The other befriends some of the apes but is feared by most. After being put through ape trial he escapes with a female human native to the planet. After helping his ape friends escape a religious heresy trial he escapes out into the wilderness with the female. There he learns the planet might not be so distant after all...