Tree House Mystery

Four brave siblings were searching for a home – and found a life of adventure! Join the Boxcar Children as they investigate the mystery of a secret window in this illustrated chapter book series beloved by generations of readers.

A family moves into the house next door! The Boxcar Children decide to make friends with their new neighbors by building a tree house with them. In the process, they notice a window in their neighbor's house that nobody knows about. Does the old home have a secret?