Daniel Stamm's documentary-style horror presents the spine-chilling footage shot by film-maker Iris Reisen (Iris Bahr) and her cameraman (Adam Grimes) following the Reverend Cotton Marcus (Patrick Fabian).
Marcus is a Louisiana evangelist famed for his ability to drive demons from the possessed. However, aside from the mental respite he brings the afflicted, he has become disillusioned with the process, seeing his own 'skills' as little more than well-meaning tricks.
Already on the verge of ending this work, he is easily persuaded to collaborate with Reisen on a film that is designed to reveal that exorcism has nothing at all to do with divine intervention.
And, when he is asked to help Nell (Ashley Bell), a troubled teenager who intermittently appears to host violent forces that mutilate the local livestock, they think they have the perfect case for his final exorcism.
But, after arriving at the isolated farm where she lives with her father (Louis Hertham), they gradually begin to wonder whether what they have before them is a deeply disturbed young woman... or something genuinely much more sinister.
The convincing performances help to slowly ratchet up the tension, while Bell's astonishing contortions - performed for real, without the assistance of CGI - lend the possession scenes an unsettling veracity.
(2010) Cert: 15