
Part of the fun of watching the movie is finding out exactly who this guy is and how he even got there. I won't spoil it since its part of the experience. The movie is effective, and if you have the slightest bit of claustrophobia, this movie might stretch your tolerance to the limit.
The movie is worth a watch, but you might end up with a hollow feeling by the movie's end--a feeling of pointlessness. As most movies go, it's all about the journey, not the end.