Young Arthur Radley's troubles start when, as a teen, he begins to run around with the wrong crowd--specifically, "some of the Cunninghams from Old Sarum." One night while cruising Maycomb in a borrowed "flivver"--an old Model-T Ford--the boys harrass a town official and lock him in the courthouse outhouse. The boys are later charged with various crimes, including disorderly conduct, disturbing the peace, assault and battery and "using abusive and profane language in the presence and hearing of a female." All of the boys but Arthur were sent to the state industrial school, but the elder Radley refused to allow his son to be incarcerated. Mr. Radley promised the judge that he would see that his son behaved, and "Mr. Radley's boy was not seen again for fifteen years." Young Arthur was forced into reclusiveness by his strict father, and he earned his moniker "Boo" because of the gossip and tales that followed his unusual existence in the Radley house.
In the book To Kill a Mockingbird Boo Radley had been seen around town sometimes with his mother when he was little. His father was a mean spirited man who was very religious. He kept tight control of his wife and two sons. His wife was seldom seen except to pour water on her flowers and every now and then to shop.
Mr. Radley would walk into town daily. One day Boo stabbed him in the leg. Boo was arrested. Mr. Radley was angry and told the judge that they would take care of their own problems. The judge kept Boo locked up for a month and then released him to his father.
Boo was a man with a simple mind. The reader does not know if he was mentally ill, mentally retarded or both. However, after the stabbing incident no one ever sees Boo again until the night that he kills Bob Ewell to protect the children. After Mr. Radley dies his son Nathan continues to serve as Boo's warden of he home. Boo eventually becomes more and more reclusive until he sees the children.