A group of astronauts, led by George Taylor (Charlton Heston), crash land on a strange planet where mute humans are treated as slaves by intelligent apes. Taylor is hunted down and captured by horse-riding gorillas, and then taken for experimentation by sympathetic chimpanzee Dr Zira (Kim Hunter). When Zira discovers Taylor's intelligence, she and her fiancé Cornelius (Roddy McDowall) appeal to the governing council on his behalf, but the appeal fails, leaving the astronaut no choice but to go on the run. Fleeing for his freedom, Taylor soon makes a shocking discovery about the provenance of this strange planet.