Most of the speculative descriptions and stories about Boo Radley come in the first chapter of To Kill a Mockingbird. Jem and Dill had grown accustomed to living nearby the Radley Place, and since they had never seen Boo, they never expected to. It was Dill's arrival in Maycomb that touched off their greatest curiosities.
The Radley Place fascinated Dill... it drew him as the moon draws water, but drew him no nearer than the light-pole on the corner, a safe distance from the Radley gate. There he would stand... staring and wondering.
Author Harper Lee gives a four-page history of the Radleys through Scout's narration, describing the known "facts" and stories (mostly from Miss Stephanie) about Boo, prompting Dill to ask
"Wonder what he looks like?"
Jem gives a "reasonable description of Boo," spurring Dill's curiosity only further. When Dill decides that he wants to
"... try to make him come out... I'd like to see what he looks like..."
the remainder of the children's summer activities seem to center only on Boo.