Tom Sawyer, an orphan, lives with his Aunt Polly and his half-brother Sid in the fictional town of St. Petersburg, Missouri, sometime in the 1840s. A fun-loving boy, Tom skips school to go swimming and is made to whitewash his aunt's fence for the entirety of the next day, Saturday, as punishment.

In one of the most famous scenes in American literature, Tom cleverly persuades the various neighborhood children to trade him small trinkets and treasures for the "privilege" of doing his tedious work, using reverse psychology to convince them it is an enjoyable activity. Later, Tom trades the trinkets with other students for various denominations of tickets, obtained at the local Sunday school for memorizing verses of Scripture. Tom then exchanges the tickets with the minister for a prized Bible, despite being one of the worst students in the Sunday school and knowing almost nothing of Scripture, eliciting envy from the students and a mixture of pride and shock from the adults.

Tom falls in love with Becky Thatcher, a new girl in town and the daughter of a prominent judge. Tom wins the admiration of the judge in the church by obtaining the Bible as a prize but reveals his ignorance when he is unable to answer basic questions about Scripture. Tom pursues Becky, eventually persuading her to get engaged by kissing him. Their romance soon collapses when she discovers that Tom was engaged to another schoolgirl, Amy Lawrence and that Becky was not his first girlfriend.

Shortly after Becky shuns him, Tom accompanies Huckleberry Finn, a vagrant boy whom all the other boys admire, to a graveyard at midnight to perform a superstitious ritual designed to heal warts. At the graveyard, they witness a trio of body snatchers, Dr Robinson, Muff Potter and Injun Joe, robbing a grave. Muff Potter is drunk and eventually blacks out, while Injun Joe gets into a fight with Dr Robinson and murders him. Injun Joe then appears to frame Muff Potter for the murder. Tom and Huckleberry Finn swear a blood oath not to tell anyone about the murder, fearing Injun Joe would somehow discover it was them and murder them in turn. Muff Potter is eventually jailed, assuming he committed the killing in an act of drunkenness and accepting of his guilt and fate.