Night of the Demon

American psychologist Dr. John Holden is in London to attend a conference on the dark arts - witchcraft, the occult, devil worship, the paranormal among other such areas - which he and his colleagues at the conference are trying to debunk. Upon his arrival in London, Holden learned that one of his colleagues, Dr. Henry Harrington, was just killed by electrocution in what is deemed an accident, however many believing, due to his research and other evidence at the scene of his death, that he was actually killed by a demon. Those who believe the demon theory also believe that Dr. Julian Karswell, the leader of a devil cult, was behind the killing using those dark arts he claims exist, he who both Harrington and Holden, the latter still, were going to denounce as a fraud at the conference in whatever powers he possesses or claims to possess playing off the superstitions of his faithful followers. One of those who believes the demon theory is Harrington's niece, kindergarten teacher Joanna Harrington in having no other logical explanation for her uncle's body being mutilated as it was when it was found. As Holden and Joanna are brought into Karswell's realm, there are veiled threats from an otherwise genial Karswell that Holden will face the same fate as Harrington, the date and time specified. Holden vehemently stands by his beliefs on the dark arts and Karswell's threats, even in the face of he experiencing things he cannot explain. But as some doubt begins to creep into his psyche, Holden, with Joanna by his side, has to figure out a way to protect himself from whatever may happen at that date and time.