Caught on film by a photographer in the company of his supermodel girlfriend, Elena, billionaire Pierre Levasseur tries to convince his wife that he’s innocent. Fearing an expensive divorce, his lawyer convinces him to find François Pignon, a young courier who also appears by chance in the photo, to get him to pretend Elena is his mistress. When Pierre promises her he will soon leave his wife, Elena agrees to move in with François. Unfortunately, this creates tension with his roommate, Richard, and his girlfriend, Émilie. Things get even more complicated when Elena begins to feel affection towards François and meddles in his personal life.