Jem & Scout are always walking by the Radley's house when coming from school. But they have never seen Boo Radley come out of the house, so they are very surprised when they find little presents inside a small hole in the tree. The summer before they were scared of entering their property but tried to a few times.
When their father, Atticus Finch, is appointed to defend Tom Robinson, a black man who is acused of having raped Mayella Ewell, Jem & Scout have to deal with being called "nigger-lovers" by classmates and adults in town.
It seems like the entire town is in the court house. Atticus establishes that Mayella and Bob Ewell are lying and under a fair trial Tom would have been free. But in this time there's no chance when a black man's word is against a white ones.
In the night of Halloween Bob Ewell attacks Jem & Scout on their way home. They can only escape and run home because a unknown man helps them and in a fight kills Bob Ewell. Later Scout recognises the unknown man as Boo Radley and sees life from his perspective.