Clues to an elaborate assassination plot are intercepted in Paris and the authorities believe the assassin's lair lies in Soho, London. Heloise Chancey, courtesan and professional detective, must go undercover to spy upon the nest of suspects and end their murderous conspiracy Meanwhile, her Chinese maid, Amah Li Leen finds herself trapped in a deadly nightmare of deceit and madness. Will she be able to escape before time runs out? Danger keeps Heloise close company as she hunts evil down to its devilish source.