As Tom Sawyer begins, Tom’s aunt, Polly, calls his name. She looks all over her house and yard, but she cannot find him. When he finally appears, she realizes that he has been in the closet eating jam he was not supposed to touch. She gets out a switch to whip him for disobeying—but at the last moment before she strikes, Tom tells her to watch out behind her. As soon as she turns to look, he runs out the door and hops over the fence.

Aunt Polly laughs to herself and puts the switch away. She tells herself that Tom will not grow up properly if she continues to let him get away with everything he does wrong. But he is her dear sister’s son, and she “ain’t got the heart to lash him somehow.” She resolves to punish him tomorrow by making him work all day.

That afternoon, Tom skips school to go swimming. Aunt Polly suspects this, so she checks his shirt collar, which she sewed shut in the morning. When she finds it still sewed, she is “half glad that Tom [has] stumbled into obedient conduct for once.” But Sid, Tom’s half-brother, points out that Aunt Polly sewed the shirt with white thread, whereas it is now sewn with black. Once again, Tom runs out the door to avoid punishment. As he leaves, he threatens to beat Sid up when he returns.

Outside, Tom soon forgets his troubles. Remembering that he has just learned to whistle, he struts down the street practicing. He meets a new boy—a rare and fascinating sight in his small town. The boy is dressed up in a dainty cap and expensive clothes, just as if it is Sunday. He is even wearing shoes. Tom takes in this “finery” and decides that he and this boy will be enemies. By way of introduction, Tom says, “I can lick you!” The boy dares him to try, but Tom just teases. When the boy demands to know why he does not make good on his threat, Tom says, “By jingoes, for two cents I will do it.” The boy pulls two pennies out of his pocket and offers them. This arrogance is too much for Tom, who slaps the coins to the ground and provides the "licking" he promised.

When the fight is over, with Tom the clear winner, the new boy runs home crying. Tom follows and lingers by the gate, teasing. When he finally goes home, it is late, so he sneaks in through the window. Unfortunately, he finds Aunt Polly waiting for him in his room. When she sees how dirty his clothes are, she renews her resolve to make Tom spend his Saturday doing work.