Joséphine (Jocelyne Desverchère) leads a serene life with her partner Antoine (Emmanuel Finkiel) and their two sons, Louis (Yvain Bougie) and Basile (Louis Dewynter). However, her stability is upended when she discovers that Antoine is having an affair with his young intern (Valérie Donzelli). Overwhelmed by hurt, rage, and a desire to dismantle her domestic boredom, Joséphine fabricates an elaborate lie: she claims to have been embarking on secret, compulsive sexual encounters with anonymous men—including a "sadistic lover" (Jean-Louis Loca). To keep up the facade, she deliberately engineers situations that heighten Antoine's suspicion and jealousy. As Antoine grows increasingly unravelled by the thought of her infidelity, Joséphine forces him to confront his own betrayals and double standards before revealing the truth to salvage their relationship.