Abby and Libby - two young girls murdered. Investigators are searching for the killer using their biggest clue: a recording of his voice from one of the victims' phones ordering the girls Down the Hill. Almost three years later, it's a mystery that still haunts the small town of Delphi, Indiana...and the police say the killer may walk among them.To learn more about how HLN protects listener privacy, visit cnn.com/privacyLearn more about your ad choices. Visit podcastchoices.com/adchoices