John, Lord Clayton, the heir to the 6th Earl of Greystoke, and his wife Alice are shipwrecked on the Congolese coast. John builds a home in the trees, and Alice gives birth to a son. She later grows ill from malaria and dies. While John is grieving her, the treehouse is visited by Mangani apes, one of whom, Silverbeard, kills him. Kala, a female ape carrying her dead infant, hears the cries of the human baby in his crib. She adopts the boy and raises him as a member of the clan as he grows up naked, wild, and free.
At age twelve, the boy discovers the treehouse. He finds a wooden block painted with pictures of a boy and a chimpanzee. Seeing himself in a mirror, the boy recognizes that he is different from the rest of his ape family. He also discovers his father's hunting knife. The objects fascinate the boy, who takes them with him. One day, his mother is killed by a native hunting party, and he kills one of them in a rage before they can kill him as well.
Years later, Belgian explorer Phillippe d'Arnot is traveling with a band of British adventurers along the river. A band of natives attacks the party, killing everyone except Phillippe. Injured, he hides in the trees. The young man in a loincloth finds Phillippe and nurses him back to health. D'Arnot discovers the man is a natural mimic and teaches him rudimentary English. After deducing who this man's father and mother are, d'Arnot calls him "Jean". John agrees to return to England with him and reunite with his human family.
On arrival at Greystoke, the family's country estate in Scotland, John is welcomed by his grandfather, the 6th Earl of Greystoke, and his ward, a young American called Jane Porter. The Earl still grieves the loss of his son and daughter-in-law but is very happy to have his grandson home. He behaves eccentrically and often seems to think his grandson is his son.
The locals treat John as a novelty, and some see his behavior as threatening. He befriends a mentally disabled worker on the estate and, in his company, relaxes into his natural ape-like behaviour. Jane, meanwhile, teaches John more English, French, and social skills. They become very close and one evening make love in secret.
At a ball held to celebrate the return of his biological grandson, an intoxicated Lord Greystoke slides down a flight of stairs and dies from a head injury. John inherits his title as Earl of Greystoke. Jane helps John through his grief, and they become engaged. He is also cheered up when Phillippe returns. One day, while visiting London's Natural History Museum with Jane, John is disturbed by the taxidermied animal displays. He discovers many live, caged apes from Africa, including his adoptive father, Silverbeard. John releases Silverbeard, but police and museum officials soon pursue them. They reach a park, where a trooper fatally shoots Silverbeard. John is devastated.
Sickened by a society that mistreats their fellow animals as well as itself, and tired of nobles who only want to use him to further their own agendas, John decides to return to Africa. Phillippe and Jane escort him back to his jungle, where he reunites with his ape family. Jane does not join him, but Phillippe hopes they may someday be reunited.
In August 1974 producer Stanley Jaffe announced Warner Bros. Pictures had bought the rights to the Tarzan character from the Edgar Rice Burroughs estate and wanted to make a new Tarzan film. "It won't be a caricature or a popularization", he said. "It will be a serious period action adventure true to the characters and done in terms of contemporary mores." Robert Towne signed to write the script. No director or cast was attached but the producer said "I expect the Tarzan we'll cast won't be a muscle man."
Towne later recalled, "I called up a friend and said, "Let's do it."
Reception
The film grossed $45.9 million upon its release, making it the 15th most popular film at the box office in 1984.