Set against the background of the Great Depression in the Deep South, in a fictitious town called Maycomb, Harper Lee's novel is on one level an amusing story about a couple of little kids growing up in this setting, but on another, more serious level, it is a commentary on how people treat and mistreat each other based on perceived differences and hypocrisy. Lee is sometimes mentioned in the same company as William Faulkner in terms of her ability to evoke the flavor and nuances of Southern culture.
There are a couple of subplots, but the main plot of this novel concerns the trial of Tom Robinson, a black man falsely accused by the town's thuggish, but white, Bob Ewell of assaulting his daughter, Mayella Ewell. There are elements of foreshadowing as early as the Christmas before the trial when Scout takes after her cousin Francis, who has gotten wind of Atticus's assignment to defend Robinson and is referring to him (Atticus) as a "nigger-lover". Scout and Jem are advised by their father that this will likely occur, and that they are to turn the other cheek. The night before the trial, Atticus is nearly attacked by a mob that tries to take Robinson from the town jail for a lynching. The trial the next day is obviously one that should be decided in Tom's favor; every shred of evidence points to Bob Ewell's lies--and it is poignant when Jem pumps his fist and says "We've got 'em"; he thinks that the weight of evidence being what it is, it's obvious Robinson will be freed--but of course, he is a black man accused by a white man, which, in Alabama in 1933 means he will be convicted. This plot continues as Robinson tries to escape prison and is shot and killed, Ewell stalks Robinson's widow, and then tries to kill the Finch kids. The final turning point occurs when Scout sees Arthur Radley in Jem's room where he is unconscious. From there, the falling action wraps up the story once and for all, as Scout stands on the Radley porch remembering the scenes of the last few years as Arthur must have seen them.