After Taylor, the astronaut from Planet of the Apes, does not return to Earth, Brent is sent after him. With the help of Cornelius, Zira, and Nova Brent must face an atomic bomb worshiping cult, escape the militaristic gorillas, and find Taylor.
The only film in the original series of five that does not star Roddy McDowall, who was committed to another project. Archive footage of McDowall as Cornelius is played at the start, and David Watson plays the character in the film proper. Despite this, McDowall is often pictured on video and DVD packaging for this film.