On February 13, 2017, the senseless murders of adolescent girls Abby Williams and Libby German left the residents Delphi, Indiana shaken. Four years later, investigators are still searching for the killer using their biggest clues: a grainy picture and recording of his voice from the victim's phone ordering the girls "Down the Hill." Based on the blockbuster podcast, HLN investigates the evidence and clues to hunt for who killed Libby and Abby.