Hitchcock employs many of the thematic and cinematic elements of earlier film genres; in particular that of German Expressionism.
This essay will argue that Hitchcock uses the Expressionist device of the doppelganger or double to delve into the darker areas of the human mind. The brilliance of Hitchcock's employment of this in "Shadow of a Doubt", it will be argued, lies in Hitchcock's realization that the monstrous is intimately linked and may in fact be produced by, normality.