Jem and Scout are terrified Ewell will attack Atticus. Atticus, thinks Ewell has already gotten the need for revenge out of his system, though Aunt Alexandra isn't so sure.
Atticus grants even Ewell the respect of trying to understand his position.
Meanwhile, Tom Robinson is in prison. Atticus thinks he has a good shot of winning on appeal. If he loses, though, Tom will be executed. When Jem expresses disdain for the jury that convicted Tom, Atticus says that one man on the jury, a Cunningham, almost voted for acquittal. This news inspires Scout to declare she's going to invite Walter Cunningham to dinner, but Aunt Alexandra forbids it. She says the Finches are too good for the Cunninghams.
Though Miss Maudie's point that Maycomb is changing is persuasive, that change is slow. Even after the obvious lessons the trial taught about the idiocy and danger of racist prejudice, Aunt Alexandra continues to hold onto her prejudices about class difference.
Later that night, Scout and Jem try to figure out why people are prejudiced. They come up with all sorts of reasons but none seems sufficient. Jem realizes Boo Radley stays in his house because he wants to.
Again, the kids' inability to understand prejudice proves prejudice makes no sense. The adult world is corrupt and senseless, and that's why Boo wants nothing to do with it.