The fifth and final episode in the Planet of the Apes series. After the collapse of human civilization, a community of intelligent apes led by Caesar lives in harmony with a group of humans. Gorilla General Aldo tries to cause an ape civil war and a community of human mutants who live beneath a destroyed city try to conquer those whom they perceive as enemies. All leading to the finale.

A young archaeologist believes he is cursed by a mask that causes him to have weird nightmares and possibly to murder. Before committing suicide, he mails the mask to his psychiatrist, Dr. Barnes, who is soon plunged into the nightmare world of the mask.