A young girl nicknamed Scout recounts her family history. She tells about her father, Atticus Finch, who became a lawyer in the town of Maycomb. Jem is Scout’s brother, and Calpurnia helps raise them after their mother dies. The siblings befriend a boy named Dill who suggests that they lure Boo Radley, a reclusive neighbor, out of his house. When Dill convinces Jem to run over and touch the house, Scout thinks that she sees a shutter move, as if someone were peeking out.
Scout eagerly attends school for the first time, but she and her teacher, Miss Caroline, do not get along. Jem invites the poor Walter Cunningham to lunch who douses his food in molasses, shocking Scout to the point that Calpurnia scolds her for not being a better hostess. Back at school, an incident involving Burris Ewell, a boy from an even poorer and less respectable family than the Cunninghams, disillusions Scout further. She asks if Atticus could teach her instead, and though he refuses, he promises to keep reading to her.
When school breaks for the summer, Dill returns to Maycomb, continuing his games with Scout and Jem and eventually creating one called “Boo Radley” that they suspend when Atticus catches them. As Jem and Dill grow closer, Scout spends time with Miss Maudie Atkinson, who tells Scout that the rumors about Boo Radley are false. On Dill’s last day in Maycomb, Scout, Jem, and Dill peer through windows at the Radley Place. They rush home after hearing a shotgun to find the neighborhood adults talking about how Mr. Nathan Radley shot at a Black man in his yard.
On Scout’s walks home from school with Jem, they find gifts left for them in a tree knothole. Maycomb endures a real winter, allowing the children to build a snowman that looks so much like Mr. Avery that Atticus demands them to disguise it. That night, Scout is woken up to find that Miss Maudie’s house is on fire, and while outside someone drapes a blanket over her, which they later realize was Boo Radley’s doing. Jem reveals the whole story of the knothole and the presents, and Atticus tells them to keep it to themselves.
Scout nearly starts a fight when a classmate uses a racial slur to declare that Atticus defends Black people, particularly Tom Robinson, who was accused of raping a white woman. Atticus says that Tom is innocent but doomed, since it’s inconceivable that an all-white jury would acquit him. One day, Atticus surprises Jem and Scout when he shoots a mad dog from a considerable distance. Mrs. Dubose, a cantankerous old lady, tells the children that Atticus is not any better than the people he advocates for, causing Jem to lose his temper and destroy all of Mrs. Dubose’s camellia bushes. As punishment, Jem goes to her house every day to read to her, and when she dies because of her morphine addiction, she leaves Jem a box with a single camellia.
Jem begins spending less time with Scout, telling her that she should act more like a girl, a comment that upsets her. The children are taken to Calpurnia’s mostly Black church, where they learn that Tom Robinson was accused by Bob Ewell. When they return home, they find Aunt Alexandra, who has come to stay with the Finches, believing that they need a “feminine influence” around the household. When Atticus tries to lecture the children on their ancestry, per Alexandra’s request, he only succeeds in making Scout cry.
Tom Robinson’s trial draws near, and Atticus’s role as his defense lawyer subjects Jem and Scout to town gossip. Scout gets into a fight with Jem after he asks her not to antagonize Alexandra, and when she goes to bed, she finds Dill hiding underneath it. Sherriff Heck Tate appears at the Finch home and expresses concerns about the possibility of a lynch mob arising as Tom Robinson is being moved to the Maycomb jail. Atticus sits outside of the jail reading, and when a group of men threaten Atticus to move, Scout intervenes.
People from all over the county make an appearance at the trial, except for Miss Maudie who does not approve of watching. Jem, Scout, and Dill sneak into the courtroom and find seats in the balcony where Black people are required to sit. Bob Ewell gives his testimony, telling the court how he found Tom Robinson raping his daughter Mayella, and Atticus asks why no doctor was called. Atticus has him write his name, pointing out that Bob is left-handed and that a left-handed man would be more likely to leave bruises on the right side of a girl’s face.
During Atticus’s fiery cross-examination of Mayella, Mayella yells at the courtroom to convict Tom Robinson, eventually crying and refusing to answer any more questions. Tom’s testimony explains how he often would help Mayella with chores, and how on the night of the alleged rape, it was actually Mayella who attempted to pursue Tom. When Bob appeared, forcing Tom to flee, Bob threatened to kill Mayella. Link Deas is thrown out of the courtroom when he defends Tom. Dill becomes so upset that Scout has to take him out of the courtroom.
Scout and Dill speak to Mr. Dolphus Raymond who tells them that he pretends to be a drunk to provide other white people with an explanation for why he prefers Black people. Atticus gives his closing remarks in the courtroom, and when he finishes, Calpurnia tells him that the children have not been home. The children beg to hear the verdict, but they are sent home. The jury eventually delivers a guilty verdict. The following day, Miss Maudie invites the children over to her house, and Jem rallies against the injustice of the verdict. Miss Maudie consoles him by telling him that Judge Taylor assigned Atticus to the case, and that the jury’s long deliberation constituted a sign of progress in race relations.
After Bob Ewell makes threats against Atticus’s life, Atticus tells his family not to worry. Jem and Atticus discuss the justice of executing men for rape, and how in Alabama a white man’s word always beats a Black man’s. Atticus shares that Tom Robinson was shot to death after attempting to escape prison. The news of Tom’s death occupies Maycomb’s attention, and an editorial is written condemning Tom’s death as the murder of an innocent man.
As school starts, the shadow of the trial still hangs over Scout. Bob Ewell, who loses his job, blames Atticus, and begins following Helen Robinson while whispering obscenities at her. Aunt Alexandra believes Bob holds a grudge against everyone connected with the trial. That Halloween, the town sponsors a pageant at the school.
On their way home from the pageant, Scout and Jem are attacked. They struggle until suddenly the assailant is pulled away and Scout stumbles home, seeing a man carrying Jem toward her house. Scout learns that Bob Ewell is lying dead under a tree and she realizes that the man who brought Jem home is Boo Radley. Heck Tate tells Atticus that though Boo is the one who stabbed Bob, Heck would rather have the whole affair hushed up to spare Boo. Scout walks Boo home, imagining the world from his perspective.