Inspiration for the story of Vampyr is credited to Sheridan le Fanu's "In a Glass Darkly". but only one story 'Carniilla" bears any relationship to the film. Rather than from any particular literary basis the film seems more to have developed from its settings (it was shot entirely on location in various deserted buildings), in which were placed a number of rather extraordinary characters living out their destiny in the shadow of a human vampire.
The structure of Vampyr is based more upon imagery than idea - the first arrival of the young man at the inn is suffused in a late afternoon greyness; the sequence of his discovery of- the building filled with mysterious shadows is in tones of white and grey. The succeeding exteriors - the young man's arrival at the chateau, his walk to the cemetery, and Leone's encounter with the vampire, are all extremely diffused so as to give a kind of preternatural mist-effect. There is no sun in the film until the final moment.
What is especially striking about Vampyr is that light and shadow become more than just contributors to a consistent style, they serve as dynamic participants in the story unfolded. Dreyer recognised that you must only suggest horror: you cannot show it, or at least, if you do, it must only be momentarily, for you cannot sustain it. ft is the audience's own imagination, skilfully probed, that provides all the horror necessary.
In what are perhaps the most uncanny and terrifying moments of Vampyr, only a wild inexplicable play of light and shadow is seen; but the terror of the malevolent supernatural force is brilliantly conveyed. One of the most effective of these moments is when the doctor, after having given the blood transfusion, leaves Leone's room and the young man runs alter him, only to reach the head of the stairs and find them empty: then we hear an abrupt crash and see the shadows cast by the staircase railings jerking crazily around on the walls of the stairwell. Throughout the film all such moments, actions communicated by purely filmic means, are left an unexplained part of the general uncanny atmosphere.