A 12th century monk with demonic intentions for Jack and the world have possessed Father Ramon Joquez!
Father Ramon Joquez has, over the past month, been translating the arcane book known as Darkhold on behalf of Jack Russell. His work now complete, the priest, filled with dread, makes a call to Jack to express his fears. The call is cut short when a mist emanating from the tome envelopes Joquez. Despite the approaching full moon, Jack drives toward Joquez's chapel, but transforms while driving the car of his friend, Buck Cowan. The Werewolf leaps out as the car crashes, and, with Jack's thoughts echoing in his head, continues toward the chapel.
There he finds Joquez, now possessed by a twelth century monk named Aelfric. The mad monk relates his origins: 800 years earlier, while in the Abbey of San Michael, he produced many scrolls containing arcane lore. Once the other monks discovered his devotion to Satan, he was burned at the stake, but the scolls, magically resistant to any damage, passed from hand to hand through the ages, with misfortune often befalling the owners. They finally ended up in the possession of Jack's father who transcribed them into a single book.
With the book now in his grasp, Aelfric intends to bring on a new dark age which he will rule. He then mystically binds Jack to a wall while he prepares.
Jack's sister, Lissa, having overheard a phone conversation between their step-father, Philip, and persons unknown, becomes more convinced Philip had a hand in their mother's fatal car wreck. Intent on telling her brother, she rushes to Buck's home, and finds the note Jack left for his friend. Lissa then heads to the chapel, but comes upon a roadblock set up to contain an area in which a deadly mist is spreading. Lissa, knowing Jack within, runs the blockade, despite witnessing police officers dissolving before her eyes. She reaches the chapel, where Aelfric finds her, and she faints, as the monk muses about the siblings' immunity to his deadly mist.
The Werewolf breaks from his mystic bonds and follows Aelfric, who conjures a minotaur-like warrior named Dragonus. The creature and the Werewolf struggle, but when Dragonus trips over his opponent's prone body, he accidentally gores Aelfric. The mad monk can longer maintain possession of Joquez's motally wounded body.
The Werewolf, finding Lissa's familiar, but unconscious, form, carries her out of the chapel.