"One of Britain's most thrilling series" (Entertainment Weekly) returns as the elite squad of detectives begin investigating a string of murders with links to the police force. Could the killer be a fellow officer? The case has deeply personal ramifications for the team led by DI David Bradford (Hugo Speer, Father Brown), involving DS Vivienne Cole's (Sharon Small, The Inspector Lynley Mysteries) ex-husband and threats to DC Rob Brady's (Bailey Patrick, Bridgerton) family. As they try to discover if a murderer lurks among their ranks, the detectives also investigate the death of a schoolboy that could be connected to a girl's suicide, a widow who somewhat suspiciously refuses to grieve, and the fatal attack on a locksmith that harks back to the manslaughter of Trainee DC Billie Fitzgerald's (Tori Allen-Martin, Unforgotten) father a decade earlier.