Following the revelations of Mrs Hudson’s past and a commission of murder in the spring of 1925, Mary Russell receives word that one of her university friends, a devout feminist, has been committed to Bedlam mental hospital. Russell herself is feeling less than balanced, and the last thing she wants is to deal with the mad. However, she agrees to look into it, when her friend escapes. The pursuit leads her across Europe to Venice and finally to the Poveglia Island, a lunatic asylum build on the bones of centuries of plague victims. Russell takes a deep breath, and follows, only to find that the lunatics may be in charge of the asylum, and nothing is quite as it seems.