This is a story with multiple protagonists, each of them narrates their angle of view of the events. They make the reader/inspector understand the event, every time, from their respective angle of view. In effect, it is a combination of three stories in one. A combination that is so unreal it can only happen in real life. If you do remember "Vantage Point" movie of Dennis Quaid, or "The Curtain: Poirot's Last Case" of Agatha Cristie, you will get the point of this story.