When a homeless man walks into Greenwich police station and confesses to a killing, it should have been the admission that cracks open a murder enquiry. Instead, he stumbles out on to the street and collapses, bleeding from a stab wound he's attempted to repair himself . . . The newest member of the Met's murder investigation team, twenty-five year-old Afghan veteran Joseph Stark, doesn't believe the man's story. Yet it becomes clear that Stark and the down-and-out share a connection. And that this could provide the key to unlocking the case. Soon, the young detective and his colleagues are drawn deeper into a dark, disturbing world as dangerous as anything Stark has known on the front line. And where there's enough at stake for a man to risk everything . . .