Historian Sydney Nathans spent most of his career studying U.S. political history and he was just making the transition to social history when he came across an intriguing letter. It was a plea written in 1859 to a North Carolina slave owner, asking for the opportunity to purchase some of the people being held in bondage. The message was sent by a white man named Peter Lesley on behalf of Mary Walker, a runaway who was once enslaved by the family she was attempting to contact. The slaves Walker wanted to purchase were her children and mother. Nathans’ curiosity about that letter, the slave woman’s request and the white man who authored it led him on a decades-long quest to find answers. The history he uncovered has been recorded in a new book, “To Free a Family: The Journey of Mary Walker” (Harvard University Press/2012). Nathans joins host Frank Stasio to talk about his findings and what Walker’s story illustrates about the power of family and community.