Perhaps you're thinking of:
* The book Scout and Jem find in the Radley's yard: This is a collection of old, discarded items, including a "package" wrapped in brown paper. Inside, they find a few trinkets and a carved soap doll. This is a significant moment in the story, highlighting the mysterious nature of Boo Radley and his interactions with the children.
* The "moon" imagery in the book: The moon is a recurring symbol in the novel. It's often associated with themes of innocence, mystery, and the passage of time. For example, the children often play in the moonlight, and Boo Radley is often seen "watching" them from his house under the cover of darkness.
If you can provide more context about what you remember about the book, I might be able to help you pinpoint the specific detail you're looking for.