Chateau Under Siege by Martin Walker is part of the Bruno, Chief of Police series and although some relationships were explained, I think it would be easier for the reader to start with the first book.
From the cover:
The town of Sarlat, France is staging a reenactment of its liberation from the British in the Hundred Years War when the play's hero is stabbed and feared fatally wounded. Bruno is tasked with the safety of his old Silicon Valley buddies, in town for a reunion. One friend goes missing and Bruno suspects there may be a link to the French government's efforts to build a chip industry in Europe.
