A new case for husband-and-wife team Patrick Gillard and Ingrid Langley: When DCI Derek Harmsworth is killed in a car crash, DI John Gray, known to be a bit of a maverick, is convinced that Harmsworth was silenced because he was investigating the violent murder of MP Jason Giddings. When Gray himself is murdered, surely those in power will acknowledge that someone doesn't want the truth to come out. Patrick Gillard, ex-MI5 and now SOCA, and his consultant (and wife) Ingrid Langley are brought in to assess further risks to the police. They discover that DS Erin Melrose is determined to make it her personal crusade to find the killers of her bosses, Harmsworth and Gray, and it is a mission that will put her - and others - in grave danger.