Arthur Radley, also commonly referred to as Boo Radley, was a major character in Harper Lee's novel To kill a mockingbird, as well as it's 1962 film-adaptation of the same name where he was played by Robert Duvall.
Arthur was a loner who rarely left his house or even allowed himself to be seen, presumably because of the emotional damage that was inflicted upon him by his father when he was a child. Since the two children Jem and Jean Louis (Scout) Finch were usually the only ones to come close to his house, they were the only ones he had some sort of connection with. Still, he was too timid to introduce himself, so he simply chose to leave gifts for them as an act of kindness. It's implied that he followed the kids' emotional journey from a distance throughout the course of the tale, thus strengthening his fondness for them.
This emotional bond was put to test when he was forced to rescue Jem and Scout from the vengeful Bob Ewell towards the end of the story. Even though his timidness prevents him from uttering a single word, even when Scout thanks him and accompanies him home, she starts to truly understand him and the two departs as friends.
- In the book, mockingbird is used as a metaphor for good people who has been treated badly. Arthur can be compared to this archetype in several ways. He was treated poorly by his father, was the victim of many unfair rumors and preferred not to be given credit for his heroic actions because of the misery the unwanted attention would bring him.