In Harper Lee's novel To Kill a Mockingbird, Scout initially describes Boo Radley as "a malevolent phantom," and a "haint," but at the end of the narrative, Boo has taken human form as a pale man who rescues her and Jem from the malice of Bob Ewell and later takes a seat on the Finches' front porch.
During the summer before Scout begins first grade, Dill Harris, who spends the summer with his Aunt Rachel, arrives in Maycomb. With his creative imagination, many a tale is spun about the reclusive spirit that dwells inside the Radley house. One day Dill bets Jem a copy of The Gray Ghost that he will not step foot in the Radley yard, and so Jem, whose nature demands that he take dares, steps onto the Radley porch in order to touch the house. But he sees no one.
Nobody knew what form of intimidation Mr. Radley employed to keep Boo out of sight, but Jem figured that Mr. Radley kept him chained to the bed most of the time. Atticus said no, it wasn’t that sort of thing, that there were other ways of making people into ghosts.
That Boo Radley is a virtual ghost is illustrated in the way in which the children envision him, as well as the reclusive and secret conditions in which he lives. While rumors about him abound, mysteriously one night he mends Jem's pants that have been torn on the Radley fence as the terrified boy attempts escape when he hears a shotgun blast. Boo secretly lays a blanket over Scout's shoulders during a fire at night.
It is not until the final chapters that the ghostly Boo Radley, whose gray eyes are so colorless that Scout thinks he may be blind, materializes. After Bob Ewell attacks the Finch children on their way home from the school program, Boo comes to their rescue, pulling the man off the children and killing him. In an effort to protect Boo from publicity that will traumatize him by such exposure that Sheriff Tate vows to report that Ewell has fallen on his own knife.
In the end, Boo saves the lives of Jem and Scout. While Jem is tended to by the doctor and remains in bed, Boo watches Jem. Then, Scout leads him through the dark rooms onto their porch; later, she walks the frail, pale man to his own front steps and porch, and Boo turns and goes inside. After she walks Boo home, Scout stands on the Radley porch and reflects,
Boo was our neighbor. He gave us two soap dolls, a broken watch and chain, a pair of good-luck pennies, and our lives.
Scout is only saddened that she and Jem have not repaid him for his loving kindness.