Tom Sawyer lives securely with the knowledge that his Aunt Polly loves him dearly. When she scolds him or whips him, he knows that inside her breast lurks a hidden remorse. Often he deserves the punishment he receives, but there are times when he is the victim of his tattletale half brother, Sid. Tom’s cousin Mary is kinder to him. Her worst duty toward him is to see to it that he washes and puts on clean clothes, so that he will look respectable when Aunt Polly takes the children to Sunday school.
When a new family moves into town, Tom sees a pretty, blue-eyed girl with lacy pantalettes. Instantly the fervent love he has felt for Amy Lawrence flees from his faithless bosom, replaced by devotion to this new girl. At Sunday school, Tom learns that her name is Becky Thatcher. She is in school the next day, sitting on the girls’ side of the room with an empty seat beside her. Tom comes late to school that morning. When the schoolmaster asks Tom why he is late, the empty seat beside Becky catches his eye. Recklessly he confesses he stopped to talk with Huckleberry Finn, son of the town drunk. Huck wears cast-off clothing, never attends school, smokes and fishes as often as he pleases, and sleeps wherever he can. For associating with Huckleberry Finn, Tom is whipped by the schoolmaster and ordered to sit on the girls’ side of the room. Amid the snickers of the entire class, he takes the empty seat next to Becky.
Tom first attracts Becky’s attention with a series of drawings on his slate. At length, he writes the words, “I love you,” and Becky blushes. Tom persuades her to meet him at lunch. Sitting with her on a fence, he explains the possibilities of an engagement between them. Innocently, she accepts his proposal, which Tom insists must be sealed by a kiss. In coy resistance she allows Tom a brief chase before she yields to his embrace. Tom’s happiness is unbounded. When he mentions his previous tie with Amy Lawrence, however, the brief romance ends, and Becky leaves with a toss of her head.
That night, Tom hears Huck’s whistle below his bedroom window. Sneaking out, Tom joins his friend, and the two go off to the cemetery. They are about to try a new method for curing warts. The gloomy atmosphere of the burial ground fills the boys with apprehension, and their fears increase when they spy three figures—Injun Joe, Muff Potter, and Doctor Robinson. Evidently they have come to rob a grave. When the two robbers exhume the body, they begin to quarrel with the doctor about money. In the quarrel, the drunken Potter is knocked out. Then Injun Joe takes Potter’s knife and kills the doctor. When Potter recovers from his blow, he thinks he has killed Robinson, and Injun Joe allows him to believe himself guilty. Terrified, Tom and Huck slip away from the scene, afraid that if Injun Joe discovers them he will kill them, too.
Becky has not come to school since the day she broke Tom’s heart. According to rumor, she is ill. Tom loses all interest in life, brooding over what he and Huck saw in the graveyard. Convinced that Tom is ill, Aunt Polly doses him with a quack painkiller and keeps him in bed, but he does not seem to recover. When Becky finally returns to school, she cuts Tom coldly. Feeling that there is nothing else for him to do, Tom decides to run away. He meets Joe Harper and Huck Finn, and they go to Jackson’s Island and pretend to be pirates. For a few days they are happy on the island and learn from Huck how to smoke and swear. They are beginning to get homesick when they hear a cannon being fired over the river from a steamboat. Then the boys realize that the townspeople are searching for their bodies. This discovery puts a new aspect on their adventure; the people at home think they were dead. Gleeful, Tom cannot resist the temptation to see how Aunt Polly is reacting to his death. He slips back to the mainland one night and into his aunt’s house, where Mrs. Harper and Aunt Polly are mourning the deaths of their mischievous but good-hearted children. When Tom returns to the island, he finds Joe and Huck tired of their game and ready to go home. Tom proposes to them an attractive plan which they immediately decide to carry out.
With a heavy gloom overhanging the town, funeral services are held for the deceased Thomas Sawyer, Joseph Harper, and Huckleberry Finn. The minister pronounces a lengthy eulogy about the respective good characters of the unfortunate boys. When the funeral procession is about to start, Tom, Joe, and Huck march down the aisle of the church into the arms of the startled mourners. For a while, Tom is the hero of all the boys in the town. They whisper about him and eye him with awe in the schoolyard. Becky, however, ignores him until the day she accidentally tears a page in the schoolmaster’s anatomy book. When the irate teacher demands to know who tore his book, Tom confesses to save Becky from a whipping. Becky’s gratitude and forgiveness are his reward.
After Muff Potter is jailed for the murder of the doctor in the graveyard, Tom and Huck swear to each other they will never utter a word about what they saw. Afraid that Injun Joe will murder them in revenge, they furtively sneak behind the prison and bring Muff food and other cheer; but Tom cannot let an innocent man be condemned. At the trial, he appears to tell what he saw on the night of the murder. While Tom speaks, Injun Joe, a witness at the trial, springs through the window of the courtroom and escapes. For days Tom worries, convinced that Injun Joe will come back to murder him. As time goes by and nothing happens, he gradually loses his fears. With Becky looking upon him as a hero, his world is filled with sunshine.
Huck and Tom decide to hunt for pirates’ treasure near an old abandoned house. One night, they watch, unseen, while Injun Joe—who returns to town disguised as a mute Spaniard—and a companion unearth a chest of money buried under the floorboards of the house. The two frightened boys flee before they are discovered. The next day, they begin a steady watch for Injun Joe and his accomplice, for they are bent on finding the hidden treasure.
Becky’s parents give a picnic for all the young people in town, after which Becky is supposed to spend the night with Mrs. Harper. One of the biggest excitements of the merrymaking comes when the children go into the cave by the river. The next day, Mrs. Thatcher and Aunt Polly learn that Tom and Becky are missing. No one remembers having seen Tom and Becky after the picnickers left the cave. Meanwhile, Tom and Becky lose their bearings and wander through the cave’s labyrinthine passages until their last candle burns out beside a freshwater spring. To add to Tom’s terror, he discovers that Injun Joe is also in the cave.
Meanwhile, Huck keeps his vigil at Injun Joe’s lodgings in town until the disguised murderer emerges. He then follows Injun Joe and his accomplice and overhears them planning to assault the Widow Douglas. After warning a neighbor named Jones in time for the man and his sons to save the widow and chase away her would-be attackers, Huck collapses in a fever. He later recovers to learn that he is a public hero.
After Tom and Becky have been inside the cave for five days, Tom finds a way out—at a spot five miles from the main entrance. He and Becky then miraculously reappear in town, where Tom is again acclaimed a hero. To prevent others from getting lost in the cave, Judge Thatcher installs a heavy iron door at its entrance. When Tom recovers from his exhausting ordeal two weeks later and hears about the iron door, he announces that Injun Joe is inside the cave. Townspeople then rush to the cave, where they find Injun Joe lying behind the new door, dead of starvation.
Using the secret entry that he discovers, Tom later takes Huck back to the cave, where they find the treasure chest hidden by Injun Joe. It contains twelve thousand dollars in gold coins. Huck, who now has an income of a dollar a day for the rest of his life, is informally adopted by the Widow Douglas. He never would have stayed with the Widow or consented to learn her prim, tidy ways if Tom had not promised that he would form a pirate gang and make Huck one of the bold buccaneers.