An elderly curmudgeon lets out a room in his large apartment rent-free to a young student - on condition that she does everything in her power to ruin his son's marriage.
Because of his wavering health, Monsieur Henri can no longer live alone in his Paris appartment. Particularly grumpy, he ends up nonetheless accepting his son Paul's suggestion that he let one of his rooms out to a young female student. Far from falling for her charms, Henri uses her to orchestrate utter family chaos...
