Tense, harrowing, subtle...and just a teeny bit boring. Aesthetically it's beautiful, the acting is great on all sides, although Matt Smith is occasionally just Matt Smith. This is a wonderful idea, and you can really see what they tried to do with it. The problem is that the meat of the movie is just not there. Endless silences do build tension, and reinforce the atmosphere of secrecy, but honestly after an hour you'll find yourself distracted. Much more could have been made of this spectacular idea, especially with this cast, if only the script were just a little bit more dense and satisfying. Ultimately I was interested, but bored.