It’s delicious to watch Hitchcock using the camera. Not a shot is wasted, and there is one elaborate sequence in which the killer goes upstairs with his victim. The camera precedes them up the stairs, watches them go in a door, and then backs down the stairs, alone, and across the street to look at the outside of the house. This shot is not for a moment a gimmick; the melancholy of the withdrawing camera movement is one of the most touching effects in the film, despite the fact that no people inhabit it.