During the events of the preceding film "Beneath the Planet of the Apes", occurring off-screen, Cornelius (Roddy McDowall) and Zira (Kim Hunter) escaped Earth prior to its destruction when they accompanied their fellow chimpanzee Dr. Milo (Sal Mineo) in salvaging and repairing the spaceship originally used by Taylor. The shock wave of Earth's destruction sends the ship through a time warp that brings the apes to 1973 Earth, splashing down off the Pacific coast of the United States. (The backward time travel of the apes creates a time paradox which is a key element of the plot in the confrontation between the apes and Dr. Otto Hasslein: is it possible for the apes or humans in 1973 to alter the future where the apes have come from? Can the future dominance of apes be prevented from happening?)