Filmed entirely from the first-person subjective perspective (POV) of the male protagonist (Philippe Harel), the camera acts as his eyes throughout the film. He is a 39-year-old married man who meets Muriel (Isabelle Carré), a 22-year-old woman, by chance in a commercial building. Fascinated by her, he begins pursuing her, and they initiate a passionate extramarital affair. Over time, Muriel demands greater commitment, leading to increasing emotional tension, conflict, and guilt as he conceals the affair from his wife while attempting to maintain his double life.