Oystercatcher by Martin Walker

Called upon to assist in an investigation of oyster thieves at the Bay of Arcachon by the Commissaire Pleven of the Bordeaux police, beloved chief of police Bruno relishes an opportunity to momentarily reunite with the beautiful and ambitious Isabelle. Bruno is only a rural policeman, and he’s there for support and, if he’s being frank, skeptical of the whole mission. But when he and Isabelle witness strange activity out in the bay one evening--Bruno gets thrust into the center of action he had never bargained for.