We know that Boo got into trouble early on, but what teenager doesn't. We also know that in order to save "face" the Radley's secluded Boo for much of his life. When Boo snapped and stabbed his father, he was taken to the courthouse, but then he was brought home. Perhaps it was mental instability that led Boo to this, but his family couldn't deal with that. His imperfections reflected on them so he was never treated as a real human being by his family again.
There are some references in the novel that imply that the elder Mr. Radley was just plain mean. When he died and his body was carried out of the house, Calpurnia said he was the meanest man who ever breathed. This was noteworthy because Cal was not critical by nature and because she especially did not criticize white people, Maycomb being what it was. Also, when Scout talked to Miss Maudie about Boo, Maudie made the comment that you never knew what went on behind closed doors. In the context of her conversation with Scout, the implication was that Boo had been tormented and abused by his father in ways only to be imagined. Nathan Radley showed himself to be unnecessarily cruel and controlling when he cemented the tree, cutting off any communication Boo had with the outside world, including his friendship with Jem and Scout. On some level, Jem understood this. He cried when he realized what had happened.
Additionally, the Radleys were very private and rarely attended Maycomb's social functions. Although they were religious, they did not attend church but worshiped at home. Mr. Radley's occupation is never given; apparently, he did not work. According to Miss Stephanie, one day the 33 year old Boo stabbed his father in the leg with a pair of scissors and then wiped them on his own pants. The sheriff locked Boo in the courthouse basement for a while before Mr. Radley had him removed and returned to the Radley house. Following Mr. Radley's death, Boo's brother Nathan returned from Pensacola to live at his old home.
When Boo was a teenager, he and some friends got into some trouble and were going to be sent to a reformatory. Mr. Radley thought that would be an embarassment to the family, so he took Boo's punishment into his own hands, leading to Boo being locked away in the Radley house until he was an adult. When Mr. Radley died, Boo's older brother Nathan returned to Maycomb and took over the role of head of the household. The book implies that the Radley's were devoutly religious, and somehow used this to intimidate Boo into staying in the house.
Boo got into trouble one time and his father found this unacceptable. Therefore, he intended on locking Boo up in order to stop any further embarrassment. When his father died, his brother returned and was the new head of the household, but kept the same ideals as his father had kept for Boo.
Who was Boo Radley's mother? And if she died when did it happen?
Where do I find an online copy of this book?