Harleigh J. Weatherby IV leads a lonely existence in the vast Weatherby mansion under the watchful eye of his great aunt Adelaide -- until a mysterious girl named Allegra literally flies over the walls of Weatherby House and into his life.

Allegra's intense curiosity about Weatherby House forces Harleigh to think about things he's always ignored, including the long-lost treasure of the first Harleigh -- which someone is trying to steal.