A depraved religious fanatic witnesses an eerie Satanic ceremony in a mysterious castle, but the witness is unaware that the "Black Mass" is a fake, staged by the wealthy scandal publisher for the amusement of his guests. The fanatic decides that he must exorcise the participants, "cleansing" their souls of the Devil's dark influence. The self-appointed savior hunts down his unsuspecting victims one by one...and forces them to submit to gruesome, horrifying exorcism rites not practiced since the Middle Ages!