Scout starts second grade, which is as bad as first grade. One day as they walk home from school, Jem tells Scout that when he went back to get his pants, they had been mended and folded.
The folded and mended pants teach Jem that Boo is not some monster. Jem never again torments Boo.
Scout and Jem continue to find things in the knothole of the tree: twine, soap carved to look like them, gum, and a broken watch on a chain. Jem proposes they write a letter and leave it in the knothole.
Jem understands Boo is communicating through the gifts and wants to communicate back, to give thanks.
But the next day Nathan Radley cements the knothole. He says the tree was dying, but Atticus tells Jem it wasn't. Jem stares at the Radley house for a long time. Scout thinks he might be crying, but can't understand why.
Jem is starting to grow up: he understands the tragedy of Boo's efforts at communication being blocked. Scout, though, still doesn't realize who's leaving them gifts.