When a woman's body is found by the Thames river police, floating opposite the Houses of Parliament in London, it doesn't take DI Brock long to work out that she's been murdered. There are marks of a ligature around her neck, and signs that she engaged in sexual intercourse shortly before death. Further investigation reveals the woman was one of a stable of prostitutes run by a shadowy figure wanted in his native Australia. But the investigation presses other names upon Brock and Poole, and they must suffer several missed turns and pay the price for their assumptions before they get their man.