The story takes place during three years of the Great Depression in the fictional Maycomb, Alabama. It focuses on six-year-old Jean Louise Finch (Scout), who lives with her older brother Jem and their widowed father Atticus, a middle-aged lawyer. Jem and Scout befriend a boy named Dill, who visits Maycomb to stay with his aunt each summer. The three children are terrified of and fascinated by their neighbour, the reclusive Arthur “Boo” Radley. The adults of Maycomb are hesitant to talk about Boo, and for many years few have
Judge Taylor appoints Atticus to defend Tom Robinson, a black man who has been accused of raping a young white woman, Mayella Ewell. Although many of Maycomb’s citizens disapprove, Atticus agrees to defend Tom to the best of his ability. Other children taunt Jem and Scout for Atticus’ actions, calling him a “nigger-lover”. Scout is tempted to stand up for her father’s honour by fighting, even though he has told her not to. Atticus faces a group of men intent on lynching Tom. This danger is averted when Scout, Jem, and Dill shame the mob into dispersing by forcing them to view the situation from Atticus’ and Tom’s points of view.
Atticus establishes that the accusers Mayella and her father Bob, the town drunk, are lying. It also becomes clear that the friendless Mayella made sexual advances toward Tom, and that her father caught her and beat her. Despite significant evidence of Tom’s innocence, the jury convicts him. Jem’s faith in justice becomes badly shaken, as is Atticus’, when the hapless Tom is shot and killed while trying to escape from prison.
Despite Tom’s conviction, Bob Ewell is humiliated by the events of the trial, Atticus explaining that he “destroyed Ewell’s last shred of credibility at that trial”. Ewell vows revenge by spitting in Atticus’ face, trying to break into the judge’s house, and menacing Tom Robinson’s widow. Finally, he attacks the defenceless Jem and Scout while they walk home on a dark night after the school Halloween pageant. One of Jem’s arms is broken in the struggle, but amid the confusion someone comes to the children’s rescue. The mysterious man carries Jem home, where Scout realises that he is Boo Radley.