Summoned to the riverside by the desperate note of an old friend, Jem Flockhart and Will Quartermain find themselves onboard the seamen's floating hospital, an old hulk known only as The Blood. On shore a young woman, a known prostitute, is found drowned in a derelict boatyard. A man leaps to his death into the Thames, driven mad by poison and fear. The events are linked-- but how? Jem and Will's hunt for the truth takes them from the dissecting tables...