Who is Isabelle? A serial murderer, a liar, a femme fatale or a stay-at-home mother, who, since a young age, has always had to fight to survive? This is what gendarmerie captain Mathilde Delboscq wants to understand, in charge of the investigation into the death of Isabelle's husband, Pascal Bonnot. When she is called to the scene of the tragedy, this young investigator has no idea that she is about to encounter the case of her career, or even her life.