With rumors of the end times swirling, philosopher and astronomer John Dee travels to Prague in an effort to prevent one of Catherine de Medici’s seductive ladies-in-waiting from luring the Holy Roman Emperor into a crusade against England. To convince the famously occult-loving Emperor to join his side, Dee entices him with the esoteric Book of Secrets, a volume that, if decoded, could provide the chance to control the levers of heaven and earth. But Dee faces enemies at every turn, including a female codebreaker who could be the undoing of Dee and England itself.