London, 1863: prostitutes in the Waterloo area are turning up dead, their sexual organs mutilated and removed. When another girl goes missing, fears grow that the killer may have claimed their latest victim. The police are at a loss and so it falls to courtesan and professional detective, Heloise Chancey, to investigate. With the assistance of her trusty Chinese maid, Amah Li Leen, Heloise inches closer to the truth. But when Amah is implicated in the brutal plot, Heloise must reconsider who she can trust, before the killer strikes again.