While an American film crew prepares to shoot The Pope's Protocol, their latest blockbuster, at the Villa D'Este in Tivoli, new forces of ancient and modern evil gather in the shadows. Against a background of dark winter evenings before the colourful explosion of Carnival, Jane Harrison continues her quest to keep faith with Professor Caseman and ensure that good will triumph once again. Events - and her own role - will prove to be more difficult and more ambiguous than she could ever have imagined.