It is the fall of 1764, and the relations between white settlers of western Pennsylvania and Indians of the Ohio area are strained. Nevertheless, the ambitious white Colonel Bouquet and his troop of 1, 500 men march into Indian country and demand the return of whites who have been kidnapped by the Delaware Indians. True Son, a fifteen-year-old white boy who has been raised by Indians since the age of four, is one of the white prisoners who is going to be returned. True Son loves his Indian way of life and considers himself to be Indian; he has been raised to view whites as enemies and cannot imagine living with them. But although the Indians love their adopted white relatives, they agree to give them back so that they will be able to keep their land. True Son's stoic Indian father, Cuyloga, whom he idolizes, forces his stubborn and resistant son to leave with the white soldiers.
On the trip to Pennsylvania, True Son is placed under the care of Del, a strong white frontiersman who understands the Delaware, or Lenny Len api, language since he grew up near Indians. During the march, True Son is very depressed and considers committing suicide by eating the root of a May apple. Del prevents him from doing so and eventually True Son gives up the idea when his Indian cousin, Half Arrow, meets up with the party and walks along with True Son and their friend, Little Crane, whose wife is also among the white captives. The three laugh together and speak of the strange ways of white people until finally True Son must part from his Indian friends and go on to the white settlement. The company of soldiers and prisoners first passes through Fort Pitt and then moves on to Carlisle, where the white captives are returned to their families. To True Son, white civilization seems like a prison compared to the free and natural world of the Indians.
Del, however, sees the stone houses and fences as symbols of the superior white culture. When True Son is introduced to his white father, Harry Butler, he is repulsed by him and states that the man is not his father. In order to help translate for the Butlers and protect them from the potentially violent True Son, Del stays with the Butlers for a little while after True Son's return. True Son, Del, and Harry Butler travel back to Paxton township where True Son meets more of his family: his mother, Myra, who is sickly; his younger brother, Gordie; and his Aunt Kate. Myra tries to get True Son to communicate with her and say his real name, John Cameron Butler, but True Son is stubborn and refuses to acknowledge that the Butlers are his real family. The only person who does not see True Son's Indian ways as strange and upsetting is Gordie, and a relationship begins to form between the two boys.
True Son cannot sleep the night of his return because he remembers the story his Indian father told him about the 'Paxton boys,' a group of white settlers who brutally murdered some peaceful Conestoga Indians. The next day True Son meets more of his relatives, including his Uncle Wilse, who was a leader of the Paxton boys. Uncle Wilse is suspicious of True Son, and the two have a heated argument about whether the Paxton boys had the right to massacre children, an argument which results in Uncle Wilse slapping True Son across the face. True Son has a difficult time adjusting to the white culture that is forced upon him. He tries to keep his Indian soul strong and proud, but as time passes and as he loses more and more of his old freedoms, True Son eventually becomes increasingly submissive to his white family. However, just as True Son seems to lose almost all faith in ever seeing Tuscarawas again, his cousin Half Arrow secretly comes to see him one night.
True Son sneaks out with his cousin, but their reunion is bittersweet because True Son learns that Little Crane, who had accompanied Half Arrow to Paxton township, was killed by Uncle Wilse the previous night. Little Crane and Half Arrow had come looking for True Son and had told some jokes that Uncle Wilse found offensive. True Son and Half Arrow go to Uncle Wilse's house to demand an explanation, but they end up half-scalping the man and then fleeing into the night. After spending several weeks together in the wilderness, True Son and Half Arrow return to Tuscarawas, where everyone except for Little Crane's family receives them warmly. Little Crane's brother, Thitpan, calls for war against the whites, and a war party is formed that includes Cuyloga, Half Arrow, True Son, and Little Crane's family. They plan to ambush a boat of white settlers by using True Son to lure them toward the shore.
The night before the planned attack, however, True Son is shocked to learn that Thitpan has scalped a young white child. He also has a dream in which his white parents and brother are on the ambushed boat. The day of the attack True Son lures in a boat by calling out for his white 'brothers' to rescue him from starvation. However, as the boat comes closer True Son sees that there is a boy Gordie's age on the boat. He becomes frightened that Gordie may be on the boat and ruins the ambush attempt. Although Little Crane's family votes to burn True Son for his betrayal, Cuyloga saves his son from death with a very moving speech.
True Son's action, however, means that he must leave the Indians forever and can no longer be Cuyloga's son. The next day Cuyloga takes True Son to a point in the woods where they part forever, and True Son continues on, alone.