Tom Sawyer lives with his Aunt Polly and his half-brother Sid. He skips school to swim and is made to whitewash the fence the next day as punishment. He cleverly persuades his friends to trade him small treasures for the privilege of doing his work.
Tom falls in love with Becky Thatcher, a new girl in town, and persuades her to get “engaged” by kissing him. But their romance collapses when she learns Tom has been “engaged” previously to Amy Lawrence. Shortly after Becky shuns him, he accompanies Huckleberry Finn to the graveyard at night, where they witness a trio of body snatchers, Dr. Robinson, Muff Potter, and Injun Joe, getting into a fight.
Tom and Huck run away to an island. While enjoying their new-found freedom, they become aware that the community is sounding the river for their bodies. Tom sneaks back home one night to observe the commotion. After a brief moment of remorse at his loved ones’ suffering, he is struck by the idea of appearing at his own funeral. Back in school, Tom gets himself back in Becky’s favor after he nobly accepts the blame for a book she has ripped.
Summer arrives, and Tom and Huck go hunting for buried treasure in a haunted house. After venturing upstairs they hear a noise below. Peering through holes in the floor, they see Injun Joe disguised as a deaf-mute Spaniard; Injun Joe and his companion plan to bury some stolen treasure of their own. From their hiding spot, Tom and Huck wriggle with delight at the prospect of digging it up. In the meantime, Tom goes on a picnic to McDougal’s Cave with Becky and their classmates. He follows and overhears their plans to attack the Widow Douglas. By running to fetch help, Huck prevents the crime and becomes an anonymous hero.
As Tom and Becky wander the extensive cave complex for the next few days, Becky gets extremely dehydrated and starved, so Tom’s search for a way out gets even more determined. He accidentally encounters Injun Joe one day, but he is not seen by his nemesis. Eventually, he finds a way out, and they are joyfully welcomed back by their community. As a preventive measure, Judge Thatcher has McDougal’s Cave sealed off, but this traps Injun Joe inside. When Tom hears of the sealing several days later and directs a posse to the cave, they find Injun Joe’s corpse just inside the sealed entrance, starved to death.
A week later, having deduced from Injun Joe’s presence at McDougal’s Cave that the villain must have hidden the stolen gold inside, Tom takes Huck to the cave and they find the box of gold, the proceeds of which are invested for them. The Widow Douglas adopts Huck, and when he attempts to escape civilized life, Tom tricks him into thinking that he can join Tom’s robber band if he returns to the widow. Reluctantly, he agrees and goes back to her.