Twelve-year-old Dana Shannon is shocked to discover a skeleton walled up in a secret room in her family's house. Also in the room is the diary of Millicent Weaver, a Quaker woman who lived in the house with her family in 1856. With the aid of Millicent's diary, Dana and her friends discover that the house was once a station on the Underground Railroad, and the woman whose remains Dana discovered was a conductor.
Chapters in this captivating mystery alternate between Dana's efforts to find out why the body was sealed away, and the Weaver family's struggle to come to terms with the issue of slavery and the conflicts in their religion, community, and country.