Crime HLN Special 'Down the Hill' Examines Unsolved 2017 Murders of 2 Indiana Girls The HLN series, which is based on the network's hit podcast of the same name, will highlight new developments in the 2017 case By Harriet Sokmensuer Published on February 12, 2021 10:14 AM Share Tweet Pin Email Trending Videos Abigail Williams and Liberty German. Photo: facebook (2) The unsolved 2017 murders of two Indiana teen girls who were found dead after going on a nature walk will be examined in a two-night television special on HLN. The special, titled Down The Hill: The Delphi Murders, will premiere on Sunday at 10 p.m. ET/PT — the fourth anniversary of the day Abigail Williams, 13, and her best friend, 14-year-old Liberty German, were found dead. It follows an HLN investigative podcast of the same name that premiered last year. On Feb. 13, 2017, Libby and Abby were dropped off by a family member to go for a hike on a local trail. The friends were supposed to be picked up by a relative later that afternoon, but they never showed up at the pickup spot. Less than 24 hours later, authorities found the girls' bodies on the side of a creek, about one mile from the trail. Want to keep up with the latest crime coverage? Sign up for PEOPLE's free True Crime newsletter for breaking crime news, ongoing trial coverage and details of intriguing unsolved cases. Days after Libby and Abby's deaths, authorities released photos taken from Libby's cell phone that showed a man on the trail. They also released a brief audio clip of his voice, also pulled from Libby's phone, as well as a police sketch. The man was later deemed the main suspect in the girls' death, but he has not been identified. Libby and Abby are believed to have been approached by this man while out walking. Libby recorded surreptitious video evidence of the man saying the words, "Guys, down the hill." Police Investigating Murders of 2 Indiana Teens Say They're 'One Piece Away' from Solving Case A photo that was released by police in 2017 of the suspect. Indiana State Police 5 Things to Know: The Case of Slain Indiana Teens Abigail Williams and Liberty German In 2019, police released an updated sketch of the suspect, as well as a previously unheard snippet of audio recording from Libby's phone. They also unveiled a new bit of video footage of the suspect walking along the Monon High Bridge. However, no arrests have been made and a possible motive remains unknown. The series will highlight new developments in the case and feature interviews with Indiana authorities, including lead investigator Carroll County Sheriff Tobe Leazenby and lead prosecutor Nick McLeland— who tells HLN's Susan Hendricks why he refuses to call the case cold. Part one of Down The Hill: The Delphi Murders premieres Sunday at 10 p.m. ET/PT on HLN. Part two airs Monday night at the same time.