Irene is an ordinary married woman living in Amiens, in the North of France. She works in a bank where, one day, she finds herself duty-bound to strip a client of her credit card and check book for ten years. Later on, while walking in a park Irene notices a mysterious homeless woman wearing a yellow coat. At a time she witnesses her shoplifting in a store. One night, on her way back home, she is attacked by the mysterious woman.

Irene, la quarantaine, mariee avec deux enfants, mene une vie sans saveur entre la banque et son pavillon de banlieue. Un soir, elle est agressee et reste trois jours dans le coma. Son reveil est douloureux mais Irene garde peu de souvenirs de l'incident. Le lendemain, elle a un choc en decouvrant le cadavre de son agresseur, une jeune fille massacree a coups de couteau. La vie d'Irene va basculer.