People in Maycomb are terrified of the Radleys. The Radleys had three sons who got into trouble with some of the Cunningham boys when they were younger. Since Arthur (a.k.a. Boo) suffers from a mental disability, the sheriff didn't have the heart to lock him up in the regular jail with the others; so, they put him in the courthouse basement. Eventually, Mr. Radley vowed the town would never have any trouble with him again if he took him home. Arthur stayed in the house with the parents and the other boys went onto some higher education.
Additionally, the Radleys are anti-social at best. They don't go to church or meet with neighbors for coffees or tea parties. Even their shutters are shut on Sundays, which is practically a sin. Scout explains the people's feelings about Boo as follows:
"People said he went out at night when the moon was down, and peeped in windows. When people's azaleas froze in a cold snap, it was because he had breathed on them. . . A Negro would not pass the Radley Place at night. . . The Maycomb school grounds adjoined the back of the Radley lot; from the (yard) tall pecan trees shook their fruit into the schoolyard, but the nuts lay untouched by the children: Radley pecans would kill you" (9).
So the Radleys are pretty much the local urban legend and source of all crazy ghost stories. Scout overhears Calpurnia say something about the father, Mr. Radley, that verifies how some people were probably afraid of him, too.
"'There goes the meanest man ever God blew breath into,' murmured Calpurnia, and she spat meditatively into the yard" (12).
From all of the gossip and folklore, Scout gets an image in her head of quite a frightening situation for Boo Radley who lives in a curious situation under a mean father. Good thing there are people like Atticus who tell his kids to leave the neighbors alone to live as they see fit and for neighbors like Maudie who says the following:
". . . that is a sad house. I remember Arthur Radley when he was a boy. He always spoke nicely to me, no matter what folks said he did. Spoke as nicely as he knew how" (45-46).
As there might be in any neighborhood, there are the gossips, the superstitious, and the level-headed. Luckily, Scout has a few level-headed adults from whom she can glean more positive and accurate information.