The narrative of African Americans “passing” into white culture has long persisted. These stories are often tragic and filled with shame, secrecy, and the abandonment of home and family. In his new book, “The Invisible Line,” Daniel Sharfstein looks at three families that were once identified as black and are now viewed as white. These stories are ones of pride as white families reconnect with their African-American roots. Among them is the story of Isabelle Whittemore. She is the great granddaughter of a legendary African American military figure and abolitionist named O.S.B. Wall. She had no idea until recently that she was part African American. Daniel joins us from Tennessee and Isabelle joins us from Mississippi.