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.

When a charming 12-year-old girl takes on the characteristics and voices of others, doctors say there is nothing they can do. As people begin to die, the girl's mother realizes her daughter has been possessed by the devil--and that her daughter's only possible hope lies with two priests and the ancient rite of demonic exorcism.