Night of the Demon (1957) Jacques Tourneur

Dr. John Holden ventures to London to attend a paranormal psychology symposium with the intention to expose devil cult leader, Julian Karswell. Holden is a skeptic and does not believe in Karswell's power. Nonetheless, he accepts an invitation to stay at Karswell's estate, along with Joanna Harrington, niece of Holden's confidant who was electrocuted in a bizarre automobile accident. Karswell secretly slips a parchment into Holden's papers that might possibly be a death curse. Recurring strange events finally strike fear into Holden, who believes that his only hope is to pass the parchment back to Karswell to break the demonic curse.

Some superbly brooding shots of Stonehenge accompanied by a haunting speech about runic powers start what is without doubt one of the darkest and most solemnly atmospheric films ever made. The cult leader Dr Karswell is brilliantly portrayed and the film is filled with memorable dialogue, well-realized characters and powerful horrific/psychological imagery, all accompanied by a grippingly sinister soundtrack. Whether you're a horror fan or not, this is unmissable.