""The Key of the Unknown"" is a novel written by Rosa Nouchette Carey. The story revolves around a young woman named Olive Varcoe, who lives with her father and two sisters in a small village in England. Olive's life changes when she meets a mysterious stranger named Mr. Blake, who seems to know more about her family than he lets on. As Olive begins to unravel the secrets of her past, she finds herself caught up in a web of deceit and danger. Along...