He (or, less frequently, she) is the monster among us, hidden in plain sight. The psychopath represents perhaps the starkest example of the disparity between appearance and reality.

Presumably, part of what intrigued Hitchcock about psychopaths is something that intrigues many people about them: their almost confounding propensity for the most monstrous behavior imaginable combined with the appearance of utter normalcy, even banality. Among filmmakers fascinated by violent psychopathology-of which there are more than a few-perhaps none were more fascinated than Hitchcock. In other words, we like our wolves best when they do more than just bare their teeth. However, invariably the psychopaths that most capture our interest are those whose pathology manifests in overt acts of violence. Cinema no doubt has its share of characters like this-ones whose sheer rapaciousness makes them more wolf than man (in reality, rapaciousness is very much a human trait and not a lupine one, but no matter).

Shadow of a doubt visual analysis