Josh Mankiewicz talks with Andrea Canning about her latest Dateline episode, \u201cA Promise to Gloria.\u201d In 1984, Yvonne Pointer vowed to track down the killer of her 14-year-old daughter, Gloria, who was murdered on her morning walk to school. Andrea tells Josh why Yvonne\u2019s 30-year search for truth has made such an impression on her and what Yvonne is doing now to protect other young people from harm.