While traveling to Tarragona, the Bishop receives two cryptic messages from an unknown and recently murdered friar. The messages have to do with the outcomes of petitions to the papal court and could be important to the King of Aragon, who's preparing to go to war. The Bishop believes they should be delivered immediately to his Majesty. Before they reach the King, they encounter a seriously injured young man, Gilabert, who claims to be of poor descent but has the manners and bearing of a young lord. During the journey, Isaac tries to help the Bishop figure out the importance of the messages.
Historical mysteries can take some work to enjoy.
If you're not familiar with the time and place, it can be a little overwhelming to pick up a book with so many historical characters and concepts. Frankly, it took me a while to get into this mystery.