As the summer progresses, Scout and Jem notice grownups in Maycomb talking about them. Scout hears the word "rape" again, and asks Atticus what it is. He tells her.
Most adults would duck Scout's question. But Atticus is true to his beliefs: he's honest with children.
Scout's question leads to the story of going to Calpurnia's church. Aunt Alexandra is horrified. She and Atticus have an argument about Calpurnia. Alexandria thinks Calpurnia is no longer necessary. Atticus says she's part of the family.
Another instance of Alexandra's social and racial prejudice.
That night, Jem tells Scout not to antagonize Aunt Alexandra, but Scout objects to him telling her what to do. They fight. Atticus sends them both to bed. Scout steps on something while climbing into bed, and, with Jem, discovers Dill hiding under her bed. Though Dill wants to keep his presence secret, Jem tells Atticus.
Jem's decision to tell Atticus that Dill is hiding under Scout's bed marks a break with childhood. Jem used to lie to hide his and the other kid's antics from Atticus. No longer.
Atticus tells Miss Rachel Haverford where Dill is, but lets Dill spend the night. Dill sleeps in Scout's room, and tells her he ran away from home because his recently married parents aren't much interested in him and wanted him to do things on his own.
In other words, Dill's parents want him to grow up. Dill has run away from home to avoid growing up.