In To Kill a Mockingbird, what happens to Scout and Jem when they arrive at the tree?
In Chapter 7 of To Kill a Mockingbird, as Jem and Scout cross the schoolyard heading home, Jem reveals to his sister that the pants he had slipped off at the Radleys' when they were caught in the fence had been mended and were folded neatly on the fence when he returned for them. Surprised to hear this, Scout notices something in the knot-hole of the Radley tree as they pass it. "Don't take it," she warns Jem, sure that it is someone's hiding spot. She thinks that someone like Walter Cunningham sneaks off at recess and places his secret things in there to keep the older children from taking them.
But when it is there for days, the Finch children assume the articles in the tree are meant for them. In a little more than a week, they discover a package of chewing gum, then the next week there is a tarnished medal, a spelling bee award from years ago. But, later, to the children's dismay, the knot-hole has been filled with cement. A few days later, Jem encounters Nathan Radley and asks if he filled the tree hole. Mr. Radley did so, saying, "Tree's dying. You plug 'em with cement when they're sick." But, when Atticus returns home, Jem asks his father if the tree is dying, and he says it is "as healthy as you are" to Jem. Therefore, Jem concludes that Mr. Radley does not want lonely Boo to communicate with him and Scout in any way, a fact that brings tears to Jem's eyes.