Middle-classed Pierre Levasseur's (Daniel Auteuil's) life changes after he marries wealthy Christine (Dame Kristin Scott Thomas). With wealth at his beckoning, he has an affair with leggy supermodel, Elena (Alice Taglioni), and makes her his mistress. Things spiral out of control after Christine gets a photograph of both of them together along with a strange male. The only way Pierre can get out of this mess is by locating this stranger, and asking him to pose as Elena's boyfriend/spouse. He is able to locate and identify him as François Pignon (Gad Elmaleh), a valet, and pays him handsomely to enact this charade, and as a result, François and Elena move in to live in a small apartment. Chaos results when Christine hires a private eye to spy on Elena, and Pignon juggles his life between the woman he adores, Émilie (Virginie Ledoyen); this charade; his attraction towards Elena; an overly inquisitive friend, Richard (Dany Boon); while a suspicious Pierre, afraid of losing Elena to Pignon, recruits a male to spy on the couple.