After Jane Kinnear sees her lover murdered and is taken to a police safe-house, it soon becomes clear that he was an M15 informant with information about an imminent terrorist attack. DI Ray Mason is a man with a controversial past, but his effectiveness at getting results means that he's now been given the task of preventing the attack. But can be be trusted? Jane tries to piece things together, but what she doesn't know is that the killer has already found out who she is. And now he's coming for her.