18-year-old chemistry student Brittany Phillips was found sexually assaulted and strangled inside her apartment in the fall of 2004. The case turned cold quickly, despite DNA tests and interviews with hundreds of individuals. Authorities found a DNA match to an early sample, but the person was quickly cleared of the murder. DNA was collected under Brittany’s fingernails, and detectives have not found a match. 20 years after her daughter’s murder, Dr Maggie Zingman is still waiting for answers. Maggie launched a crusade across America—dubbed the 'Caravan to Catch a Killer'—crisscrossing the country in a brightly wrapped van plastered with her daughter’s photo and a tip line number. Maggie shares her story and how she is using her tragedy to help others.