A quiet building in Angouleme. Clemence Lacombe is a piano teacher. She receives home visit from her former student Mona, who she considers as her own daughter, and offer her hospitality. A scream in the night, Mona disappears. Clemence investigates and will suspect everyone in her building. Her husband Benjamin, psychiatrist, treating her at home. Medication dosage of Clémence increases. Her reason wavers. Several elements trouble her. Is she prone to hallucinations? Or is she the victim of a conspiracy who wants to silence her?