After Dill and Jem decide to peep into the window of Boo Radley's, Nathan Radley catches them in the act and steps outside with his shotgun. The boys run and urge Scout along with them; in the process of fleeing Jem catches his pants on the Radley fence so much that he must step out of them in order to escape. Then, after Dill lies to Atticus about the whereabouts of Jem's pants, Jem decides that he must retrieve his pants or risk losing the trust of his father. When Scout suggests that he just leave them there because it is too dangerous to try to retrieve them, Jem and she "part company." Scout does not understand that Jem is going to be brave although no one watches or dares him. In addition, he risks danger to prevent Atticus from being disappointed in him.
Later, Scout also learns that when Jem has returned to the Radley place, his pants had been repaired and laid across the fence, waiting for Jem to return for them. When Jem returns, he lies trembling in his bed.
In Harper Lee's To Kill a Mockingbird, in Chapter Six, Jem, Dill and Scout go to the Radley's house and are spotted by Mr. Radley, who thinks he sees a burglar and opens fire with a shot gun.
As the children run away, Scout and Dill are able to sneak under a fence because Jem holds it up, but his pants get caught on the fence and he has to leave the pants behind. When the kids casually show up where the neighbors have gathered, drawn by the gunshot, Jem is in his shorts. When questioned, Dill and Jem spontaneously come up with a tall tale about playing strip poker using matches (as cards are strictly forbidden) as the cause for Jem's missing pants. Atticus tells his son to go get the pants back, and so Jem must sneak back to the fence, even knowing that Mr. Radley could still be waiting with the shotgun. Jem knows that if he does not, Mr. Radley will find the pants where he left them, on the fence, in the morning, and everyone will know the kids were at the Radley's house. Not only would this be embarrassing, but the three kids have been firmly directed to stay away from the Radleys by Atticus. Jem expects that this incident would give Atticus cause to "spank" him.
'Atticus ain't ever whipped me since I can remember. I wanna keep it that way.'
Jem shares this with Scout when he goes out that night to get his pants—mostly because she threatens to tell Atticus that he is going. Jem leaves and Scout is on pins and needles until Jem quietly returns with his pants, silently climbs into bed and finally goes to sleep.