Based on Montague R. James' classic shiver tale Casting the Runes, Curse of the Demon (aka Night of the Demon) is an exercise in psychological terror. American Professor Dana Andrews investigates a devil-worshipping cult active in England.
The cult has apparently been responsible for more than one death in recent months, and it's all the handiwork of the group's leader, an Aleister Crowley type played by Niall MacGinnis. When Andrews comes too close to MacGinnis for comfort, the devil worshipper slips a ancient parchment into Andrews' research files.
The document carries a curse that will mean death for whoever possesses it.