In To Kill A Mockingbird, how does Dill's action for escaping to Maycomb County in Ch. 14 drive the plot?
Dill has found that he has to compete with his step-father for the attention of his mother. He feels like he's constantly being pushed away so they can have time together. They even expect him to stay out of the way. He doesn't do this so well, so he goes to the one place he feels comfortable--the Finches. Unlike Dill, Boo never had anywhere to go. He only had his family there (as far as we know) in Maycomb. Dill and Scout both discuss this as they lie in her bed before falling asleep that night.
It's also mentioned in the following link that "Scout, Atticus, and Dill all fail to live up to the expectations of society." What this sets up in the future is the unexpected actions in the last couple of chapters. First of all, no one expected Bob to go after Atticus' children. What kind of man would do that? So he fell very short of society's expectations. The other character was Boo. No one expected him to even come out, let alone save the children's lives. Society never expected that, and most never knew it happened in order to save Boo from being the "hero."