Sonia, a quiet woman with an unremarkable life, is assaulted one night on the train. The shock leaves her silent, but something shifts inside her. Slowly, her gaze hardens, her movements grow sharper, more deliberate. An obsession takes hold : to find that man again. She watches him, follows him, learns every detail of his life. Until one day, their paths cross once more and this time, Sonia is no longer the same.