In Manchester, Anders Svensson is on the trail of drug baron Merlin and his lieutenant Flow, a man so dangerous his type is said to appear only once in a decade. In Glasgow, faced with the highest murder rate in Europe, Karen McCluskey is on a one-woman mission to end gang warfare. In London, Pilgrim finds he's no longer feared. Troll, the child soldier, is terrorizing the streets. This is our hidden urban underworld - untold, till now.