Claire's confession about their shared tragedy sends John reeling, and both crumble in the aftermath of a disastrous attempt to nail the prime suspect. When John is suspended from duty, Claire with her direct connection to one of the killers must put aside her guilt and fight to prevent another murder. DSI Lola Keir takes the investigation back to square one; Claire exploits a suspect's obsession; and John risks professional annihilation in the race to catch a killer. For Claire, the final confrontation will test her emotions beyond anything she's endured so far. As she finally confronts her own role in the crimes, will she finally put an end to the darkness or has the true horror only just begun?