Essex, Christmas Day: As the residents of a small town enjoy their mince pies, shots ring out in the street. Five people are gunned down before the lone shooter turns his weapon on himself. Grace Fisher, now Detective Inspector, is tasked with making some sense of this atrocity, but as she investigates it becomes clear that there is a police connection. As the evidence of corruption grows and she is obstructed at every turn, Grace knows she is walking further into danger. Then, her young key witness disappears...