The Last Exorcism plunges into the horror documentary genre pioneered by movies like The Blair Witch Project, which makes things scarier because, y'know, what if it's real, man? Director Daniel Stamm easily draws us in with that trope not because he can make us jump—which, of course, he can—but because he makes his world surprisingly, well, funny: The deliberately campy moments and the Reverend Cotton Marcus's (Patrick Fabian) Shakespearean asides to the camera engage us in a world that we'd make fun of, too. Cotton knows exorcism is a scam, and he's not even sure if he believes in God anymore. Every time Stamm's characters dose us with a candid bit of honesty, we relate a little bit more to the increasingly bad situation unfolding. That's why it's much, much scarier when REAL SHIT goes down.
We follow the filmmakers and Cotton down to the Sweetzer farm, where Louis controls his children Caleb and Nell with a penitent faith. Nell (Ashley Bell) is just so goshdarn happy about her wooden recorder and collage art that we feel really terrible when she's feeling all gurgly from maybe-possession. Cotton performs a hilarious fauxorcism for the benefit of the camera people; Nell is cleansed for a tidy fee. But even afterward, Nell makes threatening bloody pictures of dead things (like the filmmakers) and doesn't remember doing it. It's as if she's... actually possessed. The camera people take a light touch with the drawings: "I'm in like a million pieces," one of them remarks. Then, REAL SHIT: Fundie dad threatens them with a shotgun, demanding another exorcism. Oh, we say, he's actually kind of scary.
Rather than a host of subplots and demons, we get a claustrophobic focus on a dysfunctional family as experienced by Cotton and his fellow documentarians. This film succeeds at simmering our filmmakers in enough non-supernatural threats that we experience a thumbscrew tension until the real devil shows up, as he is wont to do. The end... sigh... totally, TOTALLY ruins this, but at least the happy anxiety between reality and fiction is solidly settled. Don't worry, it's not real. Really.