When the American novelist Denton receives a letter from a young woman, Mary Thomason, saying she's in danger and needs his help, he doubts if there's anything he can do. As famous writer with a well-documented past as a lawman in the American west, Denton is used to having mysteries laid at his door, but the letter is months old, and was only forwarded to him when the buyer of a painting found it stuck behind the frame. Presumably whatever Mary Thomason was frightened of has already happened. So why did she hide the note behind this particular painting, instead of sending it? The search for answers leads Denton into the heart of Bohemian London - the world of artists and their models, a world of brilliance and depravity, of unconventional morals and shifting sexual identities, where the border between genius and madness is hard to discern but easy to cross. And before he has learned the shocking truth, Denton will discover what it's like to be the object of a lethal obsession and endure a endure a terrifying confronation with his own demons.