A King Without Distraction (1963)

One Winter in the Ninetenth century. A mysterious crime has been committed in an isolated village of the Aubrac region. A retired prosecutor who lives there asks Langlois, a police captain, to investigate the case. The police officer accepts, settles down in the village and, by dint of obstinacy, winds up finding out who committed the murder. But, while tracking down the slayer, Langlois also discovers something very unpleasant about himself, he too loves killing...