Here, in a few taut moments, Hitchcock pulls off the neat trick of making the tacit voyeurism at the heart of a great film suddenly, frighteningly explicit. James Stewart’s wheelchair-bound character watches helplessly as his girlfriend (Grace Kelly) is attacked by Raymond Burr’s Lars Thorwald — and then saved by cops — in Thorwald’s apartment, clearly visible across a courtyard. Through his ever-present camera with its telephoto lens, Stewart sees Kelly give him a secret sign that Thorwald is, as they both suspected, likely guilty of killing and dismembering his wife. When Thorwald slowly looks up and gazes directly into Stewart’s camera — and into the eyes of the viewer — the sense of the watcher becoming the watched is like a punch in the gut. That the gaze belongs to a man with a discomfiting silver mane atop his head — a hairdo that would not look out of place on a schoolmarm, stalking the rows of a classroom, slapping her palm with a ruler — only makes the moment that much more disturbing.