The full plot of Escape from the Planet of the Apes runs from a flight through time to a shipyard shootout, and it ends with a swapped baby. Cornelius, Zira and Dr. Milo escape in the repaired spaceship just before Earth is destroyed, and the time warp carries them to 1973. They land near Los Angeles and are placed in the zoo, where Stephanie Branton and Lewis Dixon observe them. A zoo gorilla kills Milo.
A presidential commission questions Cornelius and Zira, who claim not to know Taylor but admit they came from the future. The government welcomes them as guests and they become celebrities. The President's science advisor, Dr. Otto Hasslein, learns that Zira is pregnant and grows afraid of what the apes' descendants might mean for humanity.
At a hearing Zira lets slip that she once dissected humans, and a truth serum then draws out her experiments and her knowledge of Taylor. The commission orders her pregnancy ended and both apes sterilized. Cornelius knocks down an orderly who mocks their unborn child, and the orderly turns out to be dead. Hasslein uses this to demand their execution, but the President insists they be taken alive.
Branton and Dixon help the apes escape to a circus run by Armando, where Zira gives birth to a son and names him Milo. As Hasslein searches circuses and zoos, Armando urges them to leave, and Dixon hides them at a shipyard and hands Cornelius a pistol. Hasslein finds them and shoots Zira and the baby, Cornelius kills Hasslein, and a sniper kills Cornelius. Zira throws the baby into the water and dies beside her husband.
The twist comes afterward: Zira had swapped her baby for another ape's, so the real Milo lives with Armando and begins to speak.
