Fou d'amour (1943)

Claude, who temporarily replaces his father at the head of a department store, falls in love at first sight with a pretty female customer. He finds out that she is named Solange and that she is the goddaughter of Professor Hauteclerc, who runs a private psychiatric hospital. To come closer to the girl of his dreams, Claude has a crazy idea: he pretends to be mad so as to be placed in Hauteclerc's institution.