"In a quiet English seaside town, antiquarian bookseller Robin Jessop has acquired an odd medieval volume. What appears to be a book isn't a book at all, but a cleverly disguised safe, in which she finds a single rolled parchment, written in code. For encryption expert David Mallory, the text is impenetrable. Until an invaluable clue opens the door to a mystery, and a conspiracy, stretching back seven centuries, when the most powerful man in Europe...