Antoine Fregoli wakes one morning with the strange feeling that the woman lying next to him is not his wife Elizabeth but another woman. Although she seems the same, he remains convinced that she is someone else.

His behaviour alters with time. He questions her about their past, refuses to sleep with her, runs into Elizabeth look-a-likes in the most improbable places, such as the operating room at the hospital where he works. Then he commits a grave medical error by walking out on a patient in the middle of an operation.

He consults a psychiatrist. He speaks with his friend and colleague Thierry who has trouble understanding his problem. Thierry puts him on sick leave to protect him from eventual punishment for having walked out on a patient.