The narrator of the book is Scout Finch, the youngest child of Atticus Finch. Scout begins by telling us of her brother's injured arm and of her family history. The earliest ancestor is Simon Finch, a fur trader who established Finch's Landing outside of Maycomb, Alabama. Scout's father is a lawyer and her mother passed away when she was two. She has an older brother named Jem. It is the summer and their neighbour's nephew Dill has come to stay for the summer. They spend the summer playing together and speculating about the Radley house. The most suspicious resident of the Radley place is Boo, who neighbours believe stalks the neighbourhood at night. Dill challenges Jem to touch the Radley house, and after a couple of days of pressure, Jem gives in.
In the fall, Dill goes back to his home in Meridian and Scout is about to begin her first year of school. Scout seems to start out on the wrong foot with her teacher, Miss Fisher. Miss Fisher is bothered that Scout reads so well. Scout explains that she has inadvertently learned from her father, and Miss Fisher requests that Scout's father teach her no more. She believes that children should learn by the school's teaching methods. Scout has also learned writing from their African-American cook, Calpurnia.
Soon after this exchange, Miss Fisher finds that Walter Cunningham has no lunch. She tries to give him money, but he will not accept. Scout tries to explain that the Cunningham's take no charity they cannot return. Scout learned this when her father took a case for the Cunningham's and they had to pay in crops, refusing to accept Atticus' generosity. Scout cannot make this concept clear and gets in more trouble with Miss Fisher.
Scout starts a fight with Walter at lunch since she blames him for getting in trouble with their teacher. Jem stops the fight and invited Walter back to their house for lunch. When at home Scout criticizes Walter for the way he eats his food, and Calpurnia scolds her for her behaviour. Back at school, Miss Caroline reacts badly to the "cooties" in a student's hair. The student is Burris Ewell, who is from an extremely poor family. She sends him home, but the class explains that Ewell children only come to the first day of school anyway. When Burris leaves, he shouts obscenities at Miss Fisher, causing her to cry. The class tries to placate her.
While walking home Scout finds two pieces of gum in the tree on the edge of the Radley lot. Later, she and Jem find two pennies in the same tree. The children have no idea who is leaving the items in the tree.
School gets out for the summer and that means the arrival of Dill. The children start coming up with games to keep them occupied. During a game, Scout is rolled onto the Radley while in a tire. This gives Jem the idea for them to pretend to be the Radley family. Atticus finds them playing in the yard and suspects that their game is at the expense of their neighbors and tells the trio to stop. Scout tells Jem that they should listen to Atticus and do what he says, but Jem thinks they can keep plying without getting in any further trouble. Scout, though, is afraid. She believes that the afternoon she rolled into the Radley yard, she could here someone inside of the house laughing at them
Scout begins to spend more time with Maudie Atkinson, their next door neighbor. She asks Miss Atkinson about Boo Radley. Miss Atkinson explains that the Radleys are very strict Baptists and they stay reclusive for religious reasons.
Meanwhile, Dill and Jem hatch a plan to give a note to Boo Radley. Dill and Scout are instructed to stand watch while Jem tries to slip the note into the house. Dill sounds the alarm that Atticus is coming down the street. The group is caught and Jem admits that they were trying to give a note to Boo. Atticus tells them to quit harassing the Radleys.