A shot rings out behind a door that gives onto a corridor in a modern building. A family - Roger the father, Nadine the mother and their son Laurent - live here. What's happened? Is it a murder? A suicide? An attempted murder? An attempted suicide? An accident? We will live with each of the three characters, one after the other, trying to discover and understand what has happened during the day prior to the incident. It's a day that begins like any other day.