In the violent world of 1874 London Sugar is a spirited prostitute in the brothel of grasping Mrs. Castaway. After her friend Elizabeth dies from injuries inflicted by two drunken clients Sugar starts writing a book to expose Mrs. Castaway's customers. Another would-be writer is William Rackham,an accountant for his father's soap factory and in debt to Dr. Curlew for the care of his unstable wife Agnes. He visits the brothel on the recommendation of friends and is impressed by Sugar's literary erudition,as well as her bedside manner.She even encourages him to do more in the family business and he becomes her regular patron. Ironically his brother Henry is smitten by Dr. Curlew's widowed sister,philanthropic Mrs. Fox,who is trying to help prostitutes to better lives. Out of interest Sugar comes to look at William's house and waves to Agnes whom she sees at a window.