A strange person named Boo Radley also lives in the town. Few people have ever seen him, but horrible miseries about him have widely spread. The children are curious about him. They tried to open his door and make him comes out, but nothing happened. Boo is surely a key character in the story, because the writer renders a mysterious atmosphere around him at an early stage. The children are going to uncover his real life, but how to do that remains unknown.
I assume that Boo Radley may