Tom Thorne's career is on the skids. Depressed by the recent loss of his father, berated for overstepping the mark on his last case, he's been 'encouraged' to take leave. It's a fairly dire situation. But not as dire as the situation for London's homeless. Three vagrants have been found murdered in the last month. Were they just random jetsam, or were they targeted for a reason?
With his deputy, Dave Holland, as his only contact, Thorne is seconded to the streets. Not as a policeman, but as one of life's rejects. It fits: he looks the part, and feels it as well. In this twilight netherworld he finds a society with its own rules and its own moral code. And the word on these streets is that the killer is a cop.