Tragedy strikes at Beaufort College when a gunman opens fire, killing several students before taking his own life; the lives of the killer's family fall apart as they try to understand what could have led their son to commit such a brutal attack.

The fingerprints found on the murder weapon set the investigators on a new track; Lea finally confesses to a secret that's been eating away at her; the investigators learn more about Jeremy's personal life.

The police make a major breakthrough and suspect Jérémy had an accomplice; as Charlie's post traumatic stress gets worse, she decides to help with the investigation and reveals some new and important details.