It is Dill's fascination with the Radley Place that spurs the children's interest in Boo. Jem and Scout are used to their reclusive neighbors--Mr. Radley never speaks and Boo is never seen--though they normally run past the Radley house when they must pass by. Dill's imagination is fueled by the stories Jem and Scout have told him, mostly gossip originating from Miss Stephanie, who claims that Boo peeks in her bedroom window at night. Scout describes Boo as a "malevolent phantom" who only comes out "when the moon was down... Any stealthy small crimes committed in Maycomb were his work." People still blame Boo for the mutilation of small animals "although the culprit was Crazy Addie." Negroes and children are afraid to pass by the Radley house, and it is rumored that Boo poisoned the pecans that fell into the schoolyard.
The more we told Dill about the Radleys, the more he wanted to know... (Chapter 1)
Dill can only wonder what Boo looks like, but Jem has a pretty good idea:
Boo was about six-and-a-half feet tall... dined on raw squirrels and any cats he could catch... his hands were bloodstained... There was a long jagged scar that ran across his face; what teeth he had were yellow and rotten; his eyes popped, and he drooled most of the time. (Chapter 1)
The children view Boo as a man to be feared, but when Dill dares Jem to run up and touch the house, claiming that he is "too scared to even put your big toe in the front yard," the Radley Place becomes all-consuming, and catching a glimpse of Boo turns into their main priority for the rest of the summer.