In what chapter of To Kill a Mockingbird does Dill's mother re-marry, preventing him from returning to Maycomb for the summer?
Dill's mother remarries in Chapter Twelve of To Kill a Mockingbird, which prevents him from returning to Maycomb for the summer as he had previously done. This change is a sad blow to Scout's spirits, as she had been desperately awaiting Dill's arrival. She receives a letter from Dill disclosing that his mother had remarried, providing him with a "new father" (whose photograph is enclosed). Dill, thus, will be staying with his family in Meridian, and his new summer plans include building a fishing boat with his new dad, who Scout describes as "a lawyer like Atticus, only much younger." Despite the fact that she misses him, she is happy that Dill has found and "caught" a father who seems to be so pleasant.
Dill promises that he will eventually come to retrieve and marry Scout as soon as he had saved up enough money, and he encourages her to write to him. Regarding this, Scout remarks,
The fact that I had a permanent fiancé was little compensation for his absence: I had never thought about it, but summer was Dilly by the fish pool smoking string, Dill's eyes alive with complicated plans to make Boo Radley emerge; summer was the swiftness with which Dill would reach up and kiss me when Jem was not looking, the longings we sometimes felt each other feel. With him, life was routine; without him, life was unbearable.
Of course, as young love often goes, Scout does not cling too steadily to her grief over the distance. She claims that she is miserable for two days but then clearly finds other ways to keep herself occupied for the summer.
In Chapter 12, Dill's mother re-marries and he does not return to Maycomb County for the summer. Dill sends Scout a letter with a snapshot of his father enclosed. Dill tells Scout in the letter that he has to stay in Meridian because he plans on building a fishing boat with his father. Scout is happy for Dill but says she feels "crushed" at the fact that she won't be playing with her best friend throughout the summer. Dill also tells Scout that he loves her, and that he will come get Scout and marry her as soon as he gets enough money. Scout laments about Dill's absence and comments that summer days with Dill were routine, and without him, life was unbearable. Scout then admits that she was only miserable for two days. Scout's comments about her childhood romance depicts Harper Lee's humor.