DI Laura Jefferson has been assigned to a dangerous task force: a team set up to bring down London’s most powerful crime boss. She and her colleagues believe they have every chance of success – until they all receive anonymous threats. They’re warned that if they don’t step back from the case they or their loved ones will be murdered. Then the killings begin. Officers and family members are picked off by a ruthless assassin at a rate of one a day. As the bodies pile up the world’s second largest police force is faced with the biggest crisis in its history.