The Exiled Prince, or The Archquisitor's Tale By Robert Reginald

"It is the year of Our Lord 1450, or 1090 by the Julian reckoning. At the royal residence in Sabbedelle, capital of the French-speaking state of Neustria, a terrible crime has been committed: the king and all of his family have been massacred. The only survivors are the monarch's younger brother, Prince Théodoric, who has fled the scene and is now accused of the crime; and the king's young daughter, Princess Melissande, who has been proclaimed Queen Regnant under the regency of the head of Neustria's Romanish church, Archquisitor Grégoire Malateste.
The hunt for Théo and his companions is led by the Archquisitor's only son, the Chevalier César de Tarde, whose ruthless pursuit of the prince drives both of them deep into the mysterious forests east of Sabbedelle. Who actually murdered the royal family? What are their motivations? Who stands to gain?
The answers will astonish and delight fantasy readers everywhere."