"The movie theater is the last bastion of society where it's acceptable to be terrified," says Eli Roth, one of the producers of The Last Exorcism, the latest horror to be unleashed by the independent film company Lionsgate. Roth, whom some will recognize with varying degrees of enthusiasm as the man behind the Hostel movies, came aboard the project early to lend his name to the publicity campaign.

Clearly excited about the prospect of "presenting" a movie rather than directing or starring in it, Roth went on to explain, at a recent press junket, how the production was guided by an overarching principle: it has to feel real. Certainly the style worked out by director Daniel Stamm reflects this ideal. The Last Exorcism bears the superficial trademarks of a low-budget documentary, replete with punchy zooms, patchy focus, and a visual strategy that involves chasing after the actors as they run through the Louisiana farmhouse where the film is chiefly set. One would have to reach back 11 years to locate its key influence, The Blair Witch Project, although Cloverfield and last year's Paranormal Activity are more recent points of comparison. "The fun of the movie is taking the conventions of The Exorcist and telling it in this realistic way," says Roth.

Cotton Marcus, played by Patrick Fabian, is the film's protagonist, and it's his documentary that we are supposedly witnessing. A fallen man of the cloth who no longer believes in the supernatural, Cotton has hired a basic camera crew to record a sham exorcism for a poor Louisiana family, thereby proving his theory. The head of the family, Louis Sweetzer (Louis Herthum), summoned the charismatic minister believing that his teenage daughter, Nell (Ashley Bell), has fallen under the sway of Satan. How else could you explain the disemboweled livestock? Certainly we, who are locked into Cotton's experience of the events, are initially skeptical. But since this is a horror movie (a Lionsgate horror movie, to be precise), and since the poster art features the lead actress twisted into odd shapes while levitating in a corner, we suspect something horrible will go down very soon. And in good time, something does.

Bell, whose creepy performance is responsible for the lion's share of shocks, was selected for the role in a most unusual way. The story goes that she impressed Stamm in the waiting room before the audition, unaware that the person querying her was the director. (Stamm admits to secretly screening his actors in this way.) Bell, double-jointed and clearly enjoying it, is called on to screw her body into discomfiting positions—a part of the job she admits was great fun.

Fabian, chosen from among a sizeable crop of actors, was asked to give an impromptu sermon as part of his audition. According to Stamm, Fabian was so convincing that the crew sat mesmerized for eight minutes as he preached nonstop, pulling random quotes and generally impressing the heck out of everybody. The success of the film hinges on his magnetism.

Some might wonder just how a movie about a possible case of demon possession could retain a PG-13 rating from the MPAA. The answer is simple, and much to the filmmakers' credit. According to Stamm, they wanted to foster an atmosphere of ambiguity so that the audience is never quite sure whether the events being depicted are of human or supernatural origin. No 360-degree head turns, no levitation (sorry, Exorcist fans). In fact, no computer generated effects or makeup of any kind. This conceit, which goes against the grain of most contemporary horror, is carried fairly far, at least until the outlandish finale, which to my mind places the film definitively in the realm of supernatural horror. But it's Stamm's willingness to straddle the line, to play both sides, that accounts for most of the tension in The Last Exorcism. Fabian puts it this way: "I've always believed in good and evil. And ghosts. I'm that kind of a guy. But I've never witnessed an exorcism. I believe people believe they are possessed. But do I think they're actually possessed by the Devil? I don't think I could answer that."