X marks the spot - and when that spot is a corpse's naked back and the X is carved in blood, DI Tom Thorne is in no doubt that the dead man is the latest victim of a particularly vicious contract kille This is turf warfare between North London gangs. Organised-crime boss Billy Ryan is moving into someone else's patch, and that someone is not best pleased. For Thorne, a tenuous link between two cases becomes two pieces of the same puzzle; past and present fuse together to form a new and very nasty riddle.

And when an X is carved on Thorne's front door, he knows that the smouldering embers of a long-dead case are about to erupt into flames….