After he and George are attacked by the vampires sent to kill Mitchell, he seems to know that the assailants in the hallway were in some way supernatural: the shock is enough to make him throw up. But in the chapel scene, he asks George if their assailants were human. If he does think that they were supernatural (and his conversation with George suggests that he does), why does he ask? * Sunnydale Syndrome. He wants George to give him another explanation, and is more than willing to let cognitive dissonance do the rest.