What happened in this section to promote valuable character and/or plot development for two characters in To Kill a Mockingbird?
The two characters who are most strongly developed during Chapters 12-15 are probably Calpurnia and Alexandra. Chapter 12 primarily deals with Jem's and Scout's visit to Calpurnia's First Purchase A.M.E. Church. Calpurnia shows the pride she has for her employer's family in several ways. She makes certain that the two children are dressed meticulously, and she defends them when they are accosted by an angry church member who does not like seeing whites in her congregation. We learn that Calpurnia is one of the few members who can read (and write), and she shows her love for the children by telling them that they can come visit her at her house " 'any time you want to.' "
When Calpurnia and the children return from church, Atticus' sister, Alexandra, is waiting for them. Unbeknownst to them all, Alexandra has come to watch over the children while Atticus is busy with the Tom Robinson trial. In the earlier chapters, we know little about Alexandra: She is bossy, thinks little of Atticus' parenting ability, but is a great cook. She displays more of these traits during Chapters 12-15, but we also learn more about her haughty pride--particularly concerning her Finch heritage. She immediately dives into Maycomb's social circles as if she was never away. She attempts to exert her control in the household by declaring that Calpurnia is no longer needed. She demands that Scout begin acting more lady-like, and Alexandra tries to shield them from knowledge about the upcoming trial. But Atticus puts his foot down and reminds her that Calpurnia is a part of the family, and that he wants his children to experience Maycomb life freely.