Astronaut Brent (James Franciscus) crash-lands on a post-apocalyptic future planet ruled by apes and finds his fellow astronaut Taylor (Charlton Heston), who is imprisoned and tortured by a group of telepathic mutants. Brent teams up with Nova, a mute human native to the planet, to evade capture by the apes and uncover the secrets beneath their sinister society. The pair soon discovers that the apes are not the greatest threat, but rather the mutated humans who worship an ancient nuclear bomb known as the "Divine Bomb" and will stop at nothing to detonate it.