Police officer Helen Weeks walks into her local newsagent's on her way to work and comes face to face with a gunman. The hostage-taker is desperate to know what happened to his beloved son, who died a year before in youth custody. By holding Helen at gunpoint, he will force a re-investigation into his son's death. Only DI Tom Thorne knows the case better than any other. As the body count rises, he must race against time to bring a killer to justice and save a young mother's life.