This is regarded as one of the genuine classics of the genre. And it’s not hard to see why - it is a perfect example of the maxim about the best horror being understated and occurring more in the mind than by depiction. The film’s director Jacques Tourneur made two of the finest films - Cat People (1942) and I Walked with a Zombie (1943) - for producer Val Lewton who patented this brand of ambiguous psychological horror.

Night of the Demon has an enormous subtlety to its horror. The film sets up a familiar 'man of reason forced to acknowledge existence of the supernatural story". (It even at one point throws in then trendy speculations about UFOs and reincarnation to, in effect, pit reason against the whole of fringe science). Tourneur bends the film cleverly - the normal daylight scenes, which are equated with reason, are directed with a monotonic flatness as though Tourneur had none but the most rudimentary interest in them. But this proves to be a subtle ploy as Tourneur is really lulling us into a false sense of relaxation for when the night-set scenes of the supernatural come, the film becomes more edgy - the eruptions of the supernatural are seen only momentarily and the camera lens itself becomes distorted as though the film itself were undergoing the hero’s journey from rationalism into panicky emotion. 

"Dana Andrews said prunes gave him the Runes", this may refer to one of his co-stars, Athene Seyler who was 70, so she may have qualified as a "prune".

American psychologist John Holden, a determined sceptic of the paranormal, arrives in London for a conference only to find his colleague Professor Henry Harrington is dead. Some of Harrington's friends believe that Harrington had a demonic curse placed on him because he was attempting to expose Satanist Julian Karswell, but Holden dismisses the notion. However as Holden encounters Karswell, he experiences a series of frightening phenomena which leave him uncertain as to whether they are real or just in his imagination. He then discovers that Karswell has passed him a piece of paper which contains a runic curse that will bring about his death in three days time unless he can pass the piece of paper onto someone else.