Night of the Demon (1957)

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.