When Abigail Williams, 13 and Liberty German, 14 go for a walk in the woods of Delphi, Indiana a series of events are kicked off that, over the next 20 hours, will set off a massive search and send families into panic. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

As the search for Abby Williams and Libby German ends at a crime scene, the reality of what's happened is worse than anyone could have imagined. A massive law enforcement presence arrives, and a double murder investigation begins. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

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 while police say the killer may walk among them. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

As the investigation forges ahead, two pictures emerge from the day of the murders: one of Abby on the bridge, taken shortly before the crime, and another of an unidentified man on the bridge, who police say they'd like to talk to. All while law enforcement swarms a property outside of town. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

More than a week after the murders, police hold a news conference that offers up new information and new evidence. But information designed to help, only deepens the mystery of what happened, and spooks everyone. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

In February 2017, Robert Ives was the prosecuting attorney in Carroll County, IN. His perspective of the crime scene, and understanding of what happened, casts some brand new light on the murders of Abby & Libby. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

To get a better understanding of what happened that day, the team goes to Delphi to walk the trail, stand at the bridge, and explore where - and how - it all happened. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

When a sketch of a suspect is released, conspiracy theories spread. The families, looking for an arrest, take their case to the national media. As the investigation goes quiet, the noise of speculation grows louder. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

For the first time in nearly two years, police release information about their investigation. It will change everything in the search for the Delphi killer. It will also leave the families and residents of Delphi looking over their shoulders. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

Three years removed from the murders of Abby Williams and Libby German, the team travels back to Delphi for new conversations, new questions and their own thoughts about what happened out there that day. To learn more about how HLN protects listener privacy, visit cnn.com/privacy

Nearly four years after the murders of Abby & Libby, HLN returns to Delphi with new questions and learns new exclusive information about the video on Libby’s phone, and new information about the case’s path forward.  To learn more about how HLN protects listener privacy, visit cnn.com/privacy