The Passion of Slow Fire (1961)

Stéphane Blanchon lives a quiet life in Switzerland with his wife, Christine, until a young American boarder named Belle, who was living with them, is found murdered. Despite Stéphane's innocence, the evidence points to him, and he learns that Belle harbored romantic feelings for him. Suspicions mount against him; even Christine thinks he is the culprit. Stéphane's sanity begins to crumble, and he lashes out in unprecedented ways.