John Holden, an American psychologist, arrived in London to attend a seminar aimed at exposing witchcraft and devil worship as a fraud, focusing on a cult hosted by Julian Karswell. When Holden got on and off the plane, he learned that the leader of the seminar, Henry Harrington, died suddenly and is now in charge. What only the audience knows is that Harrington was apparently killed by a demon, and was apparently summoned by Carlswell to retaliate for his persecution. Despite Carlswell's threatening and deceiving behavior, Holden decided to continue, although the only member of the cult who was willing to talk about his experience was in the prison psychiatric ward. He was said to be nervous after killing another member of the cult. However, according to her uncle's notes, Harrington's niece Joanna believed that Carlswell might indeed have some demonic power, which came from an ancient masterpiece in an obscure language that he could translate, and tried to warn the skeptical Hallden. Carlswell's mother also tried to warn Holden not to do so. However, Holden was initially troubled by the fact that after his encounter with Carlswell, he began to experience occasional but increasingly serious sensory and mental disorders, and found that in this encounter, Carlswell secretly slipped a piece of parchment into Holden's personal belongings, with a curse on the parchment with runic symbols, and a piece of parchment similar to that recorded by Harrington was passed to him in a similar way shortly before his death... [N.B. Holden does not live at Karswell Manor at any time].