Overjoyed to have Tom back at home, Aunt Polly is loving towards him. However, she points out that if he could cross the river on a log to go to his funeral, he could have come over to tell her that he was not dead. Mary tries to protect Tom by saying that he would have done so, if he had thought of it. Tom does not go along with this, saying that coming back to see Aunt Polly would have spoiled everything. Aunt Polly is hurt, remarking that he obviously does not love her enough. In an attempt to show that he does love her, Tom tells her that he had a dream about her. He recounts every detail of the scene he witnessed from under the bed when he visited her secretly on Wednesday night, claiming that this was his dream.
Aunt Polly is astounded by what she thinks is Tom's prophetic ability to tune in to what happened when he was not there. He changes just one detail in the account of his 'dream': he claims that he wrote Aunt Polly a note on a piece of sycamore bark saying, "We ain't dead - we are only off being pirates," and left it for her. He ends his account with the true fact that he leaned over and kissed Aunt Polly.
Aunt Polly is touched. Giving Tom a big hug, she says she forgives him everything in return for the kiss. Sid chimes in with the barbed compliment that it was kind, even if it was only a dream, but Aunt Polly tells him to shut up, saying that people do the same in a dream as they would in real life. Sid does not believe that Tom is telling the truth, but he keeps quiet. Aunt Polly sends the children off to school, and goes to tell Mrs Harper, a skeptic in matters of the supernatural, about Tom's marvelous dream.
On his way to school, Tom is greeted as a returning hero by the other children. He plays up to, and is gratified by, the adulation, which is "food and drink" to him. At school, the hero-worship continues, and reaches its height when he and Joe light their pipes.
Tom decides he no longer needs Becky: "Glory was sufficient." When Becky arrives, she shows off in an attempt to get his attention. He gives her the same treatment that she used to give him, and deliberately ignores her, talking to Amy Lawrence instead. Becky ostentatiously invites a friend to a picnic she is hosting in the vacation, hoping that Tom will overhear her. Everyone begs Becky for invitations, except Tom and Amy. Tom coolly leads Amy away.
At recess, Becky gets her revenge by sitting next to a boy called Alfred Temple and looking at a book with him. Tom is overwhelmed with jealousy and begins to be irritated by Amy's chatter. He regrets his coolness towards Becky and runs off home at noon. Without Tom to watch her and suffer, Becky becomes miserable and angrily tells Alfred to go away. Alfred realizes that he has been used in order to make Tom jealous. In revenge, he pours ink over Tom's spelling book. Becky sees this and decides to tell Tom, as a way of gaining his favor. But on her way home, she changes her mind when she remembers how Tom treated her when she was telling others about her picnic. She resolves to let him get a whipping for the spelling book, and to hate him forever.
Tom arrives home to find Aunt Polly angry with him. She has heard from Mrs Harper, who in turn heard from Joe, that Tom was indeed at Aunt Polly's house on Wednesday night and heard their talk, and that he was lying when he claimed to have dreamed it. She feels especially bad that she has been made to look a fool in front of Mrs Harper - a point that reaches home with Tom, to whom looking good in the eyes of other people is vital. She now thinks that Tom returned from the island simply to laugh at the family's troubles.
Tom feels ashamed, but insists that he did not come to laugh at her, but only "to keep you from grieving." He had intended to leave her the sycamore bark note, but became so carried away with the notion of re-appearing at his own funeral that "I couldn't, somehow, bear to spoil it," and put the bark back in his pocket. He says that he wishes now that she had awoken when he kissed her. Aunt Polly softens, and asks Tom why he kissed her. He replies, because he loves her, and because he was sorry.
Aunt Polly is touched, and believes him. She asks for another kiss before he goes off to school. Then she goes to the closet to check the pockets of his pirate jacket for the note, but, nervous of finding that Tom has lied, draws back. Finally, she plucks up courage, looks in the pocket - and finds the note. She bursts into grateful tears and says, "I could forgive the boy, now, if he'd committed a million sins!"
Tom returns to school in a warm glow of happiness. He comes upon Becky on the way, and apologizes for his behavior towards her, asking if they can be friends. She replies with scorn and says she will never speak to him again. In the schoolyard, they exchange angry words and Becky eagerly looks forward to seeing him whipped for the ruined spelling book.
In the schoolroom, Becky notices that the teacher, Mr Dobbins, has left a key in the drawer of his desk. In this drawer, which he has always kept locked, he keeps a mysterious book that he reads during quiet periods in class. Becky gives in to the temptation to open the drawer and examine the book, which turns out to be about anatomy. Mr Dobbins has always nursed an ambition to be a doctor, but has been too poor to pursue the idea.
As Becky is looking at the book, Tom comes in. Becky snaps the book shut, tearing one of the pages. She angrily blames Tom for creeping up on her, and says he will cause her to have her first ever whipping from the teacher. She also says, mysteriously and triumphantly, "I know something that's going to happen" - the whipping Tom will get for the spelling book. A flustered Tom predicts silently that the teacher will interrogate each member of the class about the torn book, that Becky's face will betray her guilt, and that she will be whipped.
The teacher notices Tom's ink-stained spelling book. Tom denies that he spilt the ink himself, but is not believed, and gets a whipping. After some time, the teacher gets out his book and notices the torn page. He asks each member of the class if they were responsible. When he gets to a terrified Becky, Tom, on impulse, leaps to his feet and shouts that he did it. Becky shoots him a look of adoration, and Tom feels so inspired that he accepts a merciless flogging from Mr Dobbins without a murmur. Tom also gets two hours detention, but he does not care because he knows Becky will wait for him outside.
Later, a shame-faced Becky tells Tom about Alfred Temple's act and her own treachery. Tom's thoughts of revenge against Alfred give way to his joy at Becky's adoring words: "Tom, how could you be so noble!"
Analysis of Chapters 19-21
Tom's behavior during Chapters 19 and 20 is both immature and self-centred. He invents the wild story of the dream in order to get himself out of a tight spot with Aunt Polly, who feels hurt that while he had no difficulty returning to St Petersburg for his own funeral, he did not bother to come back to reassure her that he was alive. He feels no remorse at lying to his aunt until she rebukes him for making her look a fool in front of Mrs Harper, to whom she recounted his apparently clairvoyant dream in good faith, unaware that Mrs Harper had heard from Joe that Tom had really returned that night. Tom, who is concerned above all else with looking good in the eyes of other people, at last understands the harm he has done to his aunt's feelings, and feels sorry.
Aunt Polly softens when he tells her that he does love her, and forgives him completely when she finds the note in his pocket that tells her that he did intend to leave a note for her. Aunt Polly feels that the fact that Tom's intentions were good is enough to excuse his behavior. She generously overlooks the fact that his reason for failing to leave the note was typically vain and morally bereft: he did not want to "spoil" his dramatic re-appearance at his own funeral. The 'dream' episode ends in Tom and Aunt Polly's genuine expression of love for each other, and Tom's genuine remorse for hurting his aunt. We feel a satisfaction in the resolution of the long thread of conflict between Tom and his aunt, and a sense that the heart is right to forgive moral transgressions in loved ones.
Aunt Polly's indulgent attitude towards Tom is set against Sid's cynicism. Sid is more psychologically astute than Aunt Polly, in that he never believed in Tom's 'dream,' but though he is right on the rational level, he is wrong on the emotional level. He dismisses Tom's claim of having kissed Aunt Polly as "only a - dream," but he is mistaken, first, because Tom really did kiss her that night, and second, because the love that prompted the kiss is real.
The atmosphere of love and forgiveness generated by Tom's reconciliation with Aunt Polly buoys him up so much that he spontaneously apologizes to Becky, with no mention of her petty behavior towards him. Tom's impulse towards selflessness confirms the ultimate wisdom of Aunt Polly's forgiving attitude.
Becky, however, does not respond positively to Tom's apology. A large proportion of these chapters is taken up with the ongoing battle between Tom and Becky, as each seeks revenge on the other for the latest insult. This is a never-ending escalating spiral of malice, which can only be broken in one way: forgiveness. Tom has learned the power of forgiveness in his exchange with his aunt, but Becky has not been through the same preparation, and rejects him. It is genuinely heroic on Tom's part to overlook even this latest display of scorn in his most self-sacrificing and noble act so far - taking the blame for Becky's 'crime' and accepting the whipping that she should have had. This naturally wins Becky over and the cycle of retribution between her and Tom is broken. Tom has grown up morally and emotionally, and has won the girl into the bargain.
The Adventures of Tom Sawyer: Novel Summary: Chapter 19 - 21