Colette, a film teacher specializing in Hitchcock's work, suspects her new neighbor across the street of murdering his wife.
Reality or professional deformation? Her husband, François, a writer of outdated historical crime novels, is at first skeptical of Colette's obsession with this alleged crime. As the clues accumulate and the mystery thickens, the ordinary couple are transformed into a pair of extraordinary detectives. So, was there really a crime on the 3rd floor?
