Jem’s mission to go and get his pants back was successful because he brought back the pants and did not get shot by Nathan Radley.
When Jem snuck onto the Radley porch, he accidentally lost his pants. He claimed to have lost them in a game of “strip poker” played with matches. The lie was intended to prevent telling anyone that they went to the Radley place, because they weren’t supposed to. Jem tells Dill that he won’t get in trouble for playing poker because Atticus would talk to his aunt.
Dill was comforted, but Jem and I weren't. There was the problem of Jem showing up some pants in the morning. (ch 6)
Jem decides to go and get his pants, despite Scout’s protests. She thinks that Nathan Radley is going to shoot him. Jem has to get the pants though, because he is worried that if Atticus finds out he lied he will lose faith in Jem. Jem is not afraid of getting punished, but he is afraid of disappointing his father.
Jem sneaks out to get the pants, and finds them and brings them back. There is something remarkable about them.
They'd been sewed up. Not like a lady sewed 'em, like somethin' I'd try to do. All crooked. It's almost like-"
"-somebody knew you were comin' back for 'em." (ch 7)
Jem is disturbed by the condition of his pants, even though he is relieved to have them back. He feels like someone was in his head, and knew what he was going to do.
He does not realize that Boo is reaching out to them until the incident of the fire, when Scout finds a blanket on her shoulders. Jem does not want to return the blanket because Boo might get in trouble. He is returning the favor.
Atticus, I swear to God he ain't ever harmed us, he ain't ever hurt us, he coulda cut my throat from ear to ear that night but he tried to mend my pants instead... (ch 8)
The incident with the pants is very important to the development of both Boo and Jem’s characters. Jem demonstrates bravery by going to face a man with a gun because he does not want to disappoint his father. Boo demonstrates bravery by reaching out to Jem in friendship, and Jem appreciates that even if it does bother him somewhat that Boo seems to be inside his head.