The movie is about repression of guild (and how it will continue to haunt you) in a tiny place in deepest Bavaria, well supported by the local rituals (which are authentic, I guess, at least I have seen similar masquerades and "devil expulsions" in Austria). At times the movie reminded me of "Angel Heart" - but situated in the blackwood forest. And the revelation is different, and - as the currently only other reviewer stated - it may be a bit too far fetched. However, this did not stop my enjoyment of the film.
Acting is flawless, Benno Fürmann is Germany's top crop and Alexandra Maria Lara (played Hitler's secretary "Traudl" in "Der Untergang") is gorgeous but still manages to fit into the image of the Hinterwädler. Thankfully the movie never looses its focus for some superfluous romance.
Not that I do not like many Hollywood productions, but this one clearly is a different breed, without being super-artistic like Hanekes "The White Ribbon" which I loved, too, and which is more profound - but also less entertaining, at least for me.
I think a fair rating for "Hinter Kaifeck" is 7.9. I rate it 9 just for some offset.