On November 4, 1980, 44-year-old Nancy Snow boarded a flight to Baltimore from St. Louis, Missouri, where she had spent several months working on Gene McNary’s U.S. Senate campaign. That night she went to a party in Baltimore; the next morning she had breakfast with the party’s host. Afterward, a man who was housesitting for Nancy apparently picked her up at a hotel, and they drove off together. Nancy Snow hasn’t been seen or heard from since then, and her disappearance is one of the D.C. area’s oldest unsolved cases. More than 44 years later, her three daughters are convinced they know who is responsible for Nancy’s disappearance.  Dateline’s Josh Mankiewicz talks with her daughters Justine, Kimberly and Stacy Snow, Corporal William Noel of the Annapolis Police Department, and retired detective David Cordle. If you have any information about the disappearance of Nancy Snow, please call the Annapolis Police Department at 410-268-9000 and ask for Corporal William Noel.