The ritual murder of a prostitute named Ada McKinley in a bedroom on decrepit Pentecost Alley would ordinarily occasion no stir in Victoria's great metropolis. But under the victim's body the police find a Hellfire Club badge inscribed with the name Finlay Fitzjames - a name that instantly draws Superintendent Thomas Pitt into the case. Finlay's father - immensely wealthy, powerful, and dangerous - refuses to consider the possibility that his son has been in Ada McKinley's bed. The implication is clear: Pitt is to arrest someone other than Finlay Fitzjames for Ada's demise. But Thomas Pitt is not a man to be intimidated, and with the help of his quick-witted wife, Charlotte, and her well-connected friends, he stubbornly pursues his investigation - one that twists and turns like London's own ancient streets....