"The ideal murderer is the one I'm waiting for". This is a phrase that Louise Arbus, an eminent university lecturer in psychocriminology, knows very well. It's taken from one of her popular books. It's also the message inscribed on the body of a victim who was found stabbed to death. A meticulously staged and dramatic crime scene that directly involves Louise Arbus. This specialist in psycho-criminology is thus forced to work with the police to solve this investigation, despite having sworn to stop eight years earlier, following the conviction of a certain Pierre Delaunay...