Chapter 8. The children's first adventure with snow serves as another step in their discovery process, and the building of the "Morphodite Snowman"--black inside and white outside--helps to advance the theme of racism found throughout the novel. When Atticus reveals that it was Boo who placed the blanket upon Scout's shoulders, the children finally realize once and for all that it is Boo who has been leaving them gifts, and that he is not to be feared. This is the final chapter of which Boo plays a major part until his dramatic return late in the novel.
Chapter 9. We learn more about life at Finch's Landing and how Alexandra's family regards Atticus's decision to take on the Tom Robinson case. Unable to follow Atticus's dictum to stop fighting, Scout loses her temper again when Cousin Francis insults both her and Atticus. The most important new information comes when Atticus reveals that Judge Taylor appointed him to defend Tom, news that is clear to the reader, but not to Scout until a future chapter. This bit of news helps in the transition toward the the main plot of Part Two: the trial of Tom Robinson.
Chapter 10. Atticus--thought to be old and feeble--can still surprise his children, and they discover his past marksmanship skills when he is called upon to kill the mad dog. The theme of innocence is advanced with the introduction of Atticus's important advice about it being "a sin to kill a mockingbird"; and Atticus's character is explored further when Miss Maudie explains about humility and why Atticus has never bragged about once being known as "Ol' One-Shot" Finch. All of this further develops the character of the man who will soon take on the dangerous assignment of defending Tom against the rape of a white woman.