Maîtresse (1976)

After breaking into a house he believes is empty, thief Olivier is caught by the owner, Ariane, who turns out to be a dominatrix. Improbably falling for her, Olivier returns periodically, and an impulsive romance blossoms despite Ariane's profession. Soon Olivier becomes more familiar with her work, even joining in on occasion. However, when he discovers that Ariane has a son, he attempts to "fix" her, hoping to give her a better life.