The Planet of the Apes starts with Leo Davidson aboard the United States Air Force space station Oberon in the year 2029. His mission involves studying primates trained for space missions. An ape named Pericles is favorite among the subjects. During a mission, Pericles’s space pod gets lost in an electromagnetic storm. Despite his superiors’ warnings, Leo follows Pericles. In his journey, his pod loses communications with the Oberon and it crashes on planet Ashlar. To his surprise, he wakes up in the year 5021 in a world ruled by apes capable of speaking the human language and humans are treated as slaves.
Leo meets a female chimpanzee named Ari. Ari buys Leo as a slave and another female human named Daena and brings them to work for her father, Senator Sandar. Leo escapes from slavery and goes about freeing other humans. When Ari finds out about his deeds, he persuades to join him in rebelling against the apes. General Thade and Colonel Attar pursue them and they end up in Calima, a forbidden but holy site for the apes.
Leo and his colleagues discover that Calima is in fact, the remains of Oberon. The computer’s logs show that at least a couple of thousands of years have passed since the crash. Furthermore, he also learns that the apes, led by Semos, took over control of the vessel after the wreck. As it turns out, the people and the apes that Leo have met are the descendant of those who were aboard Oberon.
A war between the apes and humans commences. As the battle ensues, a space pod descends from the sky. Leo recognizes Pericles’s vehicle while the apes think that their first god, Semos, have arrived.
After he lands, Pericles heads straight for the Oberon while Leo follows in. Inside the vehicle, General Thade confronts Leo. As the pair fight, Pericles tries to help Leo but to no avail. Thade snatches Leo’s gun away from him but he becomes confused as to how to use it. Grabbing this opportunity, Leo locks up Thade on the pilot’s deck of Oberon before he can shoot him. After bidding farewell, to his ape friends, Leo leaves the planet aboard Pericles’ pod. The movie ends in Leo arriving back on earth in Washington D.C. He looks up at a monumental statue bearing the face of General Thade as he is surrounded by reporters and police officers. All of them are apes.