The fourth medieval mystery featuring physician Kathryn Swinbrooke.
The year is 1471. Shortly after the murderous takeover of the throne by Edward IV and Elizabeth Woodville, blackmailers thrive by challenging detractors of the new king. The ugliest threat to the people of Canterbury is the magus Tenebrae, who controls the Book of Shadows - a grimoire of spells and magic containing secrets about the dead and the living. When Tenebrae is murdered, physician and apothecary Kathryn Swinbrooke is summoned to solve the crime, or else risk the transfer of her love, Colum Murtagh, far away to London. However, the secrets stretch all the way to the King and Queen themselves, and everyone is a suspect - especially Tenebrae's last visitors, a nervous group of goldsmiths from London. Tenebrae is dead but the Book of Shadows still exerts his power, and its new owners will die for it. As the suspects fall victim, one by one, to violent deaths, Swinbrooke most solve the mystery before the Book of Shadows closes on them all.