A tragic case that has baffled Indiana authorities for three years will get national attention on Investigation Discovery. Libby German, 14, and Abby Williams, 13, went for a walk in the woods in their small town and never came home. Their bodies were found the next day. At a loss for leads, authorities are getting help from "In Pursuit with John Walsh." For its season finale Walsh’s son Callahan goes to Delphi to tell this story. InsideEdition.com’s Mara Montalbano has more.