The novel starts out in the Alabama town of Maycomb, where Scout, Jem and their widowed father, lawyer Atticus Finch, lived during the Great Depression. During one of their summers, Jem and Scout befriend a boy named Dill who came to live in their neighborhood for the summer. While playing, Jem and Scout tell Dill of the spooky house on their street called the Radley Place. Nathan Radley owns the house, and his brother Arthur (known as "Boo") lives there also. Boo becomes a person of legend to the children as he has stayed inside the house for years without ever been seen coming out.
After their summer had ended, Scout goes to school for the first time. At the end of the day she concludes that she hates school, in that her teacher explained that she was taught incorrectly how to read by her father and that she cannot read anymore. On their way home from school, Jem and Scout discover gifts left for them in the knothole of a tree on the Radley property. Dill returns the next summer, and they begin to play pretend games that enact the story of Boo Radley. Atticus learns of this new game, and puts a stop to it, saying that they need to see it from Boo's perspective before judging him. But towards the end of summer, the three trespass on the Radley property and are shot at by Nathan Radley. In their hustle to escape, Jem loses his pants while scrambling underneath a wire fence. When he goes back to retrieve it, the pants are found mended and folded over the fence. During the next school year Jem and Scout find more presents in the tree, and suspect that Boo might be the person giving it to them. But later, Nathan Radley seals the knothole with cement. Shortly afterwards, a fire breaks out in the neighborhood, and while the children watch their neighbor's house burn, Boo slips a blanket over Scout without them noticing. Jem then tells Atticus about the gifts and the mended pants.
Meanwhile, Atticus agrees to defend an African-American man, Tom Robinson, in a case against Bob and Mayella Ewell who are accusing Robinson of rape. In the racist white society of Maycomb, the children are teased and harassed at school and even at Finch's landing during their family Christmas celebration. The children then visit a local black church with their nanny, Calpurnia, and become friends with many of the people there.
Then, one day when the children came home, they found that their aunt Alexandra has come to live with them during the next summer. And Dill is found hiding under Scout's bed because he had ran away from his "new father" from another town and into Maycomb to be with the Finches. As Tom Robinson trial begins, a mob of racist white men attempt to lynch Tom in a local jail, where they are intercepted by Atticus. The children, curious to know where and what Atticus is doing, interrupt the scene and in an attempt to be polite and friendly, Scout tries to talk to one of the men in the mob, Mr. Walter Cunningham. In this act of innocence, Cunningham disperses the mob.
At the courthouse, Robinson's trial begins as the children watch from the balcony. At the witness stand, Atticus interrogates Mayella, and obtains solid evidence of Tom Robinson's innocence. Mayella became infatuated with Tom, and in one event of their meeting, she attacks Tom in her desire of him. Bob Ewell catches the two, and beats her for being involved with a black man. To cover up her shame, they lie and accuse Robinson of rape. Despite all the facts, the all-white jury declared Tom guilty. Later, Tom attempts to escape from prison and is lethally shot.
After the trial, Bob Ewell is convinced that although he won the case, Atticus and the judge made a fool out of him. Blind with revenge, Bob stalks Tom Robinson's window, attempts to break into the judge's...