How had old Mr. Radley seen to it that his younger son, Arthur ("Boo"), caused no further trouble in Maycomb?
After young Arthur Radley fell in with the wrong crowd and was arraigned on several charges of criminal mishchief in Harper Lee's novel, To Kill a Mockingbird, he was sentenced to a stint in the state industrial school,
... where boys were sometimes sent for no other reason than to provide them with food and decent shelter: it was no prison and it was no disgrace.
However, young Arthur's father decided that no son of his was going to be handed over to state authorities, and he promised to handle the situation himself. So, the father locked young Arthur away in the Radley Place and the doors
... were closed on weekdays as well as Sundays, and Mr. Radley's boy was not seen again for fifteen years.
Then one day, "Mrs. Radley ran screaming into the streets that Arthur was killing them all." Young Arthur, now 33 years of age, had stabbed his father with a pair of scissors. Threatened with a visit to the state mental asylum in Tuscaloosa, Mr. Radley told Sheriff Heck Tate to lock him up in the jail instead, but rather than
"... put him in jail alongside Negroes... Boo was locked in the courthouse basement.
Young Arthur was eventually released to his father once more and was again locked away in the Radley house, where he was rarely seen again. His nickname, Boo, came about after the latest of the scandals.