The physical confrontation sets up a crucial theme in the novel: Evil hides in the dark, trying to kill that which is good. Bob Ewell has told Atticus that he would seek revenge against him for defending Tom Robinson in the trial, but Atticus likely didn't foresee that Bob would seek out his children. In the dark, Bob has attacked Jem and Scout with every intention of killing them. Jem has been more badly injured, and Scout is scared at first that he has died. Bob Ewell personifies evil: he has no redeeming qualities in the story and only seeks to destroy goodness.

Another theme that emerges is this: When times are tough, ordinary people can do extraordinary things. Boo Radley has lived as a recluse in his house for many years. It is clear through this scene that he has still been keeping an eye on the children who played games in and near his yard, and he knew they were in danger on this night. Boo hides himself in the woods and emerges just in time to save the kids from the danger of Bob Ewell. Boo kills Bob and takes Jem home to Atticus. After this heroic act, he doesn't emerge from his house again. His extraordinary bravery saves the kids's lives.

Many of author Harper Lee's main themes can be found in Chapter 28 of To Kill a Mockingbird. Bob Ewell's attack on the children and the subsequent appearance of Boo Radley represents the final act of Jem's and Scout's loss of innocence. The theme of courage and cowardice is found in the scurrilous decision by Bob Ewell to kill Atticus's children and the heroic actions of Boo to protect them. The theme of guilt and innocence is presented by Sheriff Tate's decision to call Bob's death self-inflicted, protecting the innocent Boo Radley of a public inquiry.

"There's a black boy dead for no reason, and the man responsible for it is dead. Let the dead bury the dead this time, Mr. Finch."  (Chapter 30)

The theme of hypocrisy can be found when the inept Colonel Maycomb, for whom the town is named, is once again celebrated despite the disaster he brought "to all who rode with him in the Creek Indian Wars." The theme of superstition vs. reality is found during the children's conversation about "Haints and Hot Steams" as they make their way in the spooky darkness to the school. And, as usual, the lack of any African Americans present indicates that the town is continuing its observation of racial segregation (the theme of prejudice and tolerance).