In a futuristic world that has embraced ape slavery, Caesar, the son of the late simians Cornelius and Zira, surfaces after almost twenty years of hiding out from the authorities, and prepares for a slave revolt against humanity.
Cornelius and Zira's son Caesar leads apes to revolution in this installment of the apes saga. Dogs and cats have been wiped out by a plague and now apes are household pets that are treated like slaves. Caesar has the intelligence to fight this oppression.
Fourth feature in the simian series has apes domesticated and turned into work slaves in the near future. Along comes Ceasar, son of Cornelius and Zira who died in the third film, who leads his chimp brothers in rebellion against the human oppressors, thus creating the time loop that leads to the first film.
- In 1983 (several years after the end of 'Escape from the Planet of the Apes'), an interstellar disease kills the world's cats and dogs, leaving humans with no pet animals. To replace them, humans began keeping monkeys and apes as household pets. In time, humans notice the apes' capacity to learn and adapt; thus they train them to perform menial household tasks. By 1991, the former United States of America and most of the North American continent has become an oppressive and fascist police superstate culture of uniformed classes and castes, based upon ape slave labor. The different apes are divided into similar caste systems; gorillas wear red jumpsuits; chimpanzees wear green jumpsuits; and orangutans wear orange jumpsuits.
In the opening scene, Armando (Ricardo Montalbán) and Caesar (Roddy McDowall), a young chimpanzee horseback rider in Armando's circus, visit a large city to distribute flyers advertising the circus' arrival to town. Armando warns the chimpanzee to be careful; should anyone learn his identity as the child of the late Cornelius and Zira, it would mean their deaths. Walking the streets, they see apes cleaning streets, delivering packages, et cetera, and are shocked by what is done to disobedient apes. Seeing an ape being beaten and drugged by black-uniformed neo-Gestapo police units, Caesar shouts: "Lousy human bastards!". Quickly, Armando takes responsibility for the exclamation, explaining to the policemen that it was he who shouted, not his chimpanzee. The surrounding crowd become agitated, and Caesar runs away.
Hiding in a stairway, Armando says he will go to the authorities and settle the matter by bluffing. Meantime, Caesar must hide among his own kind (in a cage of orangutans from Borneo), and soon finds himself being trained for slavery through violent conditioning. He then is sold at auction to the neo-Fascist Governor Breck (Don Murray). Gov. Breck allows the ape to name himself by randomly pointing to a word in a book handed to him and the chimpanzee's finger rests upon the name Caesar, as if by chance (but the audience knows that the ape can read and searched for the name). Caesar is then put to work by Gov. Breck's chief aide, the African-American MacDonald (Hari Rhodes), who sympathizes with the apes to the thinly veiled disgust of his boss, and eventually deduces Casear's true identity.
Meanwhile, Armando is being interrogated by Inspector Kolp (Severn Darden), who suspects his "circus ape" is the child of the two civilized apes from the future back in 1973. Kolp's assistant puts Armando under an authenticator machine that psychologically forces people to be truthful. Rather than confessing, Armando fights the guards and commits suicide by jumping to his death through a window. Learning of the death of the only human he loved, Caesar loses faith in human kindness and begins plotting a simian rebellion.
Secretly, Caesar teaches the combat arts to the other apes and has them gather weapons. Meanwhile, Gov. Breck learns from Inspector Kolp that the manifest of the vessel that delivered Caesar lists no chimpanzees. Suspecting Caesar is the ape the secret police are hunting, Breck's men arrest Caesar and electrically torture him until he speaks, thus betraying his identity. Hearing the confession, Breck orders Caesar's immediate death. Caesar survives his execution because MacDonald, feigning over-sensitivity to torture, reduces the electrical power of the machine. Once Gov. Breck leaves, Caesar kills the torturer and escapes.
Caesar leads an ape revolt against Ape Management and a violent and climatic 25-minute battle begins. The apes are victorious after killing most of the riot police. After bursting into Gov. Breck's command post and killing most of the personnel, Caesar has Breck marched out to be executed in the courtyard. MacDonald appeals to Caesar's humanity to show mercy to his former persecutor. Caesar ignores him, and in a rage declares:
"Where there is fire, there is smoke. And in that smoke, from this day forward, my people will crouch, and conspire, and plot, and plan for the inevitable day of Man's downfall. The day when he finally and self-destructively turns his weapons against his own kind. The day of the writing in the sky, when your cities lie buried under radioactive rubble! When the sea is a dead sea, and the land is a wasteland out of which I will lead my people from their captivity! And we will build our own cities, in which there will be no place for humans except to serve our ends! And we shall found our own armies, our own religion, our own dynasty! And that day is upon you NOW!"
However, as the apes raise their rifles to beat Breck to death, Lisa (Natalie Trundy), Caesar's beloved and later wife, voices her objection; "NO!" other than Caesar, she is the first ape to speak. Caesar reconsiders and orders the apes to lower their weapons, saying:
"But now... now we will put away our hatred. Now we will put down our weapons. We have passed through the night of the fires, and those who were our masters are now our servants. And we, who are not human, can afford to be humane. Destiny is the will of God, and if it is mans destiny to be dominated, it is Gods will that he be dominated with compassion, and understanding. So, cast out your vengeance. Tonight, we have seen the birth of the planet of the apes!"
The final shot shows Caesar standing among all his fellow gorillas, chimpanzees, and other apes among the burning buildings as the city burns to the ground.