Jem and Dill concoct a plan to leave a note on Boo Radley's window. This takes place at a time after Jem and Scout have started to drift apart. When Jem informs Scout of the plan, her response is to tell them to abandon the effort.
The idea seems dangerous to her and outlandish to her.
Scout admits to feeling terror just thinking of delivering a note to Boo Radley, but she suggests that Jem “just knock the front door down. . . .”
They don't listen. They plan to put a note on a fishing pole and reach the note over the fence and leave it on a window. The plan fails. Jem repeatedly drops the note on the ground and Dill fails to sound the alarm when Atticus approaches.
When they are caught, Atticus tells the children not to bother Boo Radley. He has a right to his privacy. Atticus is quite stern with Jem in this episode.
“What Mr. Radley does is his own business.”
This is not the last time Jem violates the privacy of the Radley house and property, but it is his last warning from Atticus. Later, the prospect of punishment or of losing the respect of his father proves to be less powerful than the mysterious draw of Boo Radley.