When Jem first informs Dill and Scout that they are going to play "Boo Radley," the concept is relatively simple. Each child will take on the role of a character in Arthur "Boo" Radley's life, which he will then act out to the best of his knowledge and ability. Scout is delegated the role of Boo's mother, Dill was to play Boo's father, and Jem was to play the part of Boo Radley himself. Early in the summer, the acting consisted of simply sweeping, walking down the street and coughing, or making "monster" noises from under the porch.
As the summer goes on, the children improve upon their acting skills and become much more dramatic in their interpretations of what they imagine has taken place in Boo's life. Their story is based on the rumors they have heard regarding Boo, as well as an inclination (not unusual in any way) to make their play as dramatic as possible. All three of the young people have vivid imagination, and they put them to good use.
By the time Atticus Finch, Scout and Jem's father, witness their playacting and puts an end to it, the trio of children have progressed to point of pretend violence; Jem acts out a "plunge into Dill's thigh." The three have also assumed various roles of "the sheriff, assorted townsfold, and Miss Stephanie Crawford." Jem and Dill are disappointed to have to stop playing "Boo Radley," but Scout is relieved.