In the summer 0f 1972, the United States launches four astronauts into space. Three men—Taylor, Landon and Dodge—are accompanied by one female astronaut named Stewart. Just before Taylor joins the other three in suspended animation on what should be an interstellar flight to explore the far reaches of the solar system, he reveals himself as overbearingly self-important and provides a subtle bit of foreshadowing by asking those in the past he has left far behind whether man is still such a lowly beast that he wages war against himself. The lecture on his own sense of self-superiority concluded, he climbs into his airtight chamber to join the others in light years of slumber.
Warning alert brings the three men out of their slumber as the craft begins to descend at a dizzying rate into a crash landing. More than two-thousand light years have passed since the craft blasted off: back on Earth the year is 3978. The exact details of where they have crashed remain unknown, only how many years have passed back on earth. This makes the Taylor, Dodge and Landon the oldest and longest-living human beings as history. As for Stewart, whom Taylor unaffectionately will describe as the “New Eve” lies rotting in her suspended animation chamber as the result of an accident; 0ld and gnarled, she has apparently laid dead for at least six months flight time and at least hundreds of light-years.
Although they crash into an enormous lake that swallows their spaceship and any hope of returning back to earth, the land around them is barren. A desert with soil incapable of producing or sustaining life. Thus they set off for greener pastures equipped with enough supplies to keep them fed for only three days. After much hiking and philosophical argument (primarily due to Taylor’s insistence on hearing the sound of his own voice) they spot what appears to be scarecrows; at the very least they are structures not created naturally. Before they barely have enough to take in the full dimension of this discovery, they spot something even more interesting: a waterfall with water that can actually be consumed. A long slow death by thirst, at least, will be avoided.
As they are swimming naked, half-seen, half-naked human steal their belongings and rifle through their clothes. The astronauts catch on, discover much of their technological advancements are now about as useful as the ship lying at the bottom of the lake and set off to find the thieves. What they are find are apparently mute and very primitive humanoids more akin to Jonathan Swift’s Yahoos than human beings. And, just as in Swift’s tales, it turns out that the smartest guys in the room are animals considered beasts back home on TV. Only instead of intellectually gifted horses holding the sub-human humans in contempt, it is gorillas on horseback. Taylor discovers he has landed on a planet ruled by apes as he gets shot in the throat shortly after discovering that Dodge has been shot to death.
When Taylor comes to in Ape City the full extent of this upside down world is revealed. It is not just gorillas that have evolved, but chimpanzees and orangutans. Taylor’s wound prevents him from talking, but he is still desperate to convince one of the chimps—a biologist named Zira—of his own intelligence. He tries to communicate with her, but a mute girl to whom he has taken a shine and with whom Zira hopes he will mate erases what he has written in the dirt to prove he is intelligent. One of the orangutans—Dr. Zaius—nevertheless manages to see some of the letters scrawled in the dirt, but obliterates them with his foot.
Dr. Zaius will turn out to be Taylor’s antagonist: against Zira’s will he will eventually order Taylor to be castrated. He will also order the lobotomy of Landon. All this evil is the result of Zaius—seemingly alone in ape society—knowing the truth about humans. Once they were as intelligent and evolutionarily advanced as apes. But—much like Taylor—Zaius knows the true nature of human being never changed: they are the only animals that kill each other for reasons other than self-preservation.
Upon learning that he is to be castrated, Taylor tries to make a run for it and when trapped in a net famously becomes the first human voice heard by living apes. His ability to speak is first attributed to a trick and then to Taylor’s being a mutant freak. Taylor is hauled before a tribunal of like-minded peers of Zaius to prove that he is anything but a freak of nature that should be put down for the sake of ape culture.
Zira and her archaeologist husband Cornelius arrange for Taylor to escape his fate and follow him to the Cornelius’ digs in the Forbidden Zone. Before he can fully escape, Zaius and gorilla goons arrive to try to capture or kill Taylor, but Taylor makes a hostage of Zaius. Inside the caves where Cornelius has been conducting digs is found an old human doll that is revealed to have the ability to say “Mama.” Since no evidence of a simian society is present at the level of the dig at which this doll was found, it appears to disprove what is contained in the Sacred Scrolls outlining the history and religious beliefs of ape evolution. Man at one point had the ability to speak and, by extension, held dominance over the planet.
Zaius agrees to let Taylor and Nova go but warns him that he is not going to like what he finds on his journey. After Taylor leaves, Zaius orders the entire archaeological dig demolished, including the evidence inside. Taylor and Nova set off on horseback and later arrive in the shadow of an enormous structure looking high over them. The structure turns out to be the head and upper body of the Statue of Liberty, blown nearly to smithereens by a powerful weapon that could only have been a nuclear weapon. The revelation falls upon Taylor like the bottom half of the statue: he has been on Earth the whole time, thrust far into its future as a planet ruled by apes after all-out nuclear war destroyed human civilization as he knew it.
