London, 1582: Mistress Rosamond Jaffrey, a talented and well-educated woman of independent means, is recruited by Queen Elizabeth I's spymaster, Sir Francis Walsingham, to be lady-in-waiting to Lady Mary, a cousin of the queen. With her talent in languages and knowledge of ciphers and codes, she will be integral to the spymaster as an intelligence gatherer, being able to get close to Lady Mary just at the time when she is being courted by Russia's Ivan the Terrible. However, there are some nobles at court who will do anything they can to thwart such an alliance; and Rosamond soon realizes the extent of the danger, when a prominent official is murdered and then an attempt is made on both her and Lady Mary's lives. In her quest to protect her ward--and her estranged husband--Rosamond must put herself in mortal peril.