Tom feels rejected and full of sorrow. He meets Joe Harper, who is also feeling sorry for himself after his mother punished him for a crime he claims he did not do. Tom persuades Joe to join him in becoming a pirate on the uninhabited Jackson's Island in the Mississippi river. Huck agrees to go too. They take a raft and steer it to the island, calling out improvised nautical commands as they go. At around 2 o'clock in the morning they land on the island, make a fire and cook some bacon that Joe Harper has stolen from home. They reflect on the life of freedom enjoyed by pirates, who do not have to get up in the mornings, go to school, and wash. Pirates, says Tom, "have just a bully time," burning ships, killing people, burying treasure and taking beautiful women to their island.
Huck makes a pipe out of a corn cob, which he loads with tobacco and smokes. The other boys envy him and resolve to begin smoking themselves. Eventually, they feel drowsy and lie down, but find it difficult to sleep because their consciences tell them that they have done wrong in running away and stealing meat. They make up their minds that their brand of piracy will exclude stealing, and then they fall asleep.
Next morning, Tom awakes and observes the bug life around him. A caterpillar crawls over him, which he superstitiously interprets as meaning he will have new clothes - a pirate's outfit. Tom wakes the others and they bathe in the river. They are happy to see that their raft has floated off, as this means that they cannot easily return to "civilization." Tom and Huck catch some fish, which they eat for breakfast.
By the afternoon, the boys are beginning to feel lonely and homesick, though none will admit it. They hear a strange booming sound and see a large number of boats on the river. The booming sound is coming from the steam ferry-boat: a cannon is being fired over the water in line with the superstitious belief that it will bring any drowned corpse to the surface. The boys realize that the townspeople are searching for them in the assumption that they have drowned. Instantly, they feel like heroes, and triumph in the thought that tears are being shed for them. But after supper, as it grows dark, they start to think of the people at home who will be missing them. Joe broaches the subject of going home, but Tom is contemptuous of the idea, and is backed up by Huck. After Joe and Huck are asleep, Tom decides to visit home to check on reactions to his absence. He writes two notes on some sycamore bark. He puts one into Joe's hat and the other in his pocket before running to the shallow water at the sand-bar.
Tom wades out along the sand-bar and swims the rest of the distance to the Illinois shore. He stows away on a ferry-boat, which takes him across the river to the St Petersburg shore. He runs to Aunt Polly's house and looks in through the sitting-room window. He sees Aunt Polly, Sid, Mary, and Joe Harper's mother, sitting talking. Tom sneaks in through the door unseen and hides under the bed. Aunt Polly is talking about him, saying that he was never bad, only mischievous, and "no more responsible than a colt. He never meant any harm, and he was the best-hearted boy that ever was." Mrs Harper says Joe was much the same. She feels remorseful because just before Joe had disappeared, she had whipped him for stealing cream, forgetting that she herself had thrown the cream out. Both women cry and wish that they had been kinder to the boys. Mary too is in tears. Sid, however, only makes critical remarks about Tom.
Tom is touched by his aunt's grief, but remains in his hiding place. He learns that the townspeople have found the raft and assumed that the boys have drowned. It is now Wednesday, and the people have decided that if the bodies are still missing on Sunday, the funerals will be held that morning.
Mrs Harper leaves and Mary goes to bed. Aunt Polly kneels and prays for Tom, then goes to sleep. Tom is about to leave his note written on sycamore bark for her when he changes his mind. He kisses his sleeping Aunt and creeps out. He takes a boat, rows back to the island, and eats breakfast with the other boys.
Analysis of Chapters 13-15
Becky's rejection of Tom prompts him to act on an earlier impulse and run away to become a pirate. In the tradition of romantic fiction, Twain is suggesting that disappointment in love can drive a man to desperate measures. That Tom has an unrealistically romanticized view of the lives of pirates is clear from his description: "Oh, they just have a bully time - take ships, and burn them, and get the money and bury it in awful places in their island where there's ghosts and things to watch, it, and kill everybody in the ships - make 'em walk a plank. they don't kill the women - they're too noble. And the women's always beautiful, too."
There is irony in this idealized picture of a life of lawless behavior without consequences. Tom has just witnessed a real incident of grave-robbing, intended extortion, murder and robbery in the graveyard. He has been unable to confront the consequences of the incident - the potential hanging of an innocent man. He has instead run away and taken refuge in the fantasy version of such crimes, in which pirates rob, murder, but adhere to chivalric codes of conduct and are "too noble" to kill women. Similarly, he has been unable to deal with his feelings for Becky in a straightforward way. A tiny glimpse of the harshness of an outlaw's life is provided by Huck, a real-life semi-outcast, who comments, "I don't ever get enough to eat gen'ally - and here they can't come and kick at a feller and bullyrag him so." He also remarks that he has only the clothes he stands up in.
Tom has previously fantasized about dying in order to make those who reject or mistreat him sorry. Tom's escape to the island enables him to live out this fantasy, as the townspeople assume that the boys are drowned. The adults, in fact, respond exactly as Tom predicted, weeping and feeling guilty for not having treated the boys more kindly when they were around. The accuracy of Tom's prediction both shows his psychological astuteness and humorously comments on the hypocrisy and foolishness of adult society, which only values a person's inherent goodness after he or she is dead. This is made clear in Chapter 15 by Aunt Polly's stern rebuke to Sid for his dismissive comments about Tom: "Sid!... Not a word against my Tom, now that he's gone!" This is the first time we have seen Aunt Polly defend Tom against Sid's malice.
The Adventures of Tom Sawyer: Novel Summary: Chapter 13 - 15