The patient is on a train, travelling to therapy, she gets off the train and lights a cigarette on the platform. A hurriedly passing man knocks into her by accident and with little reaction but a cold fury she methodically proceeds to grab, turn him and (a knife having appeared in her hand without explanation) stab him in the stomach. She holds the knife in one hand, sticking into him and holds him into the knife with the other hand on his back. He doesn't struggle from shock but judders and chokes and she continues to steady him, keeping him held to the knife. The man is fixated on her with terror, she stares coldly over his shoulder, looking bored and resigned. Eventually he goes limp and she lowers him to the floor without emotion; still not looking at him. The scene cuts back to reality - the man has just knocked into her, he regains his stance, apologises and moves on his way as she glares after him. She continues to smoke. She holds a lighter by her side and grates her thumb over it, slowly and purposefully. On the third grate the flint catches and she looks down. Blood is welling from the thumb. She looks down at it for a moment then back up and starts to smile then laugh; quietly but manically. The laughter begins to calm and then suddenly she snaps out of it, looks down. She flexes her hand; the blood is gone. She continues to stare straight forward; expressionless, inhales on the cigarette again, starts to smile once more as she exhales the smoke.
In therapy. Only the patient can be seen in shot, in the empty room, talking to her therapist who is behind the camera.
I am still toying with the possibility of having the dialogue in French (with subtitles):