Dill has already left for his home in Meridian when the chapter begins, so there is really not a great deal of new character development evident. Scout is longing for Dill already:
He was not out of mind: I missed him.
Dill and Jem still would not let Scout join them at Barker's Eddy, where Jem had finally taught Dill to swim, since the pair of boys always skinnydipped. Scout would probably not have minded, and would undoubtedly have joined them herself, but the boys wouldn't allow it. Dill promises to return to Maycomb--and Scout--"the minute school was out." Dill has revealed to Scout about Tom Robinson's wife's reaction to the news of his death (Atticus had picked the boys up on the way home from Barker's Eddy), how Helen had "Just fell down in the dirt, like a giant with a big foot just came along and stepped on her."
The relationship between Scout and Dill has grown stronger. Scout considers him her boyfriend--and fiance, since Dill has promised to marry her--and they share secret kisses when no one is looking. They had also innocently shared a bed on the night that Dill had run away from home, and Scout counts the days until school ends and Dill comes back to her.