To Kill a Mockingbird takes place in the fictional town of Maycomb, Alabama, during the Great Depression. The protagonist is Jean Louise ("Scout") Finch, an intelligent though unconventional girl who ages from six to nine years old during the course of the novel. She is raised with her brother, Jeremy Atticus ("Jem"), by their widowed father, Atticus Finch. He is a prominent lawyer who encourages his children to be empathetic and just. He notably tells them that it is "a sin to kill a mockingbird," alluding to the fact that the birds are innocent and harmless.
When Tom Robinson, one of the town's Black residents, is falsely accused of raping Mayella Ewell, a white woman, Atticus agrees to defend him despite threats from the community. At one point he faces a mob intent on lynching his client but refuses to abandon him. Scout unwittingly diffuses the situation. Although Atticus presents a defense that gives a more plausible interpretation of the evidence—that Mayella was attacked by her father, Bob Ewell—Tom is convicted, and he is later killed while trying to escape custody. A character compares his death to "the senseless slaughter of songbirds," paralleling Atticus's saying about the mockingbird.