This is really a spectacular film. I know I'm going to have to see it at least once more, because there's so much stuff going on that it's impossible to give Stay the attention in deserves in one viewing.
First and foremost, although I won't give away the plot here, I'll say that the movie (thankfully) does not rely on a surprise ending for the totality of its impact. In fact, if you're paying attention, you can pretty much figure out (mostly) what the situation is before you get too far into the movie. Unlike some of the worst examples of this genre (i.e. The Sixth Sense), Stay is not a film that "hides the ball," but instead presents you with characters and a storyline, and asks you to draw your own conclusions.
That said, there isn't an obvious solution to the movie. While you may be able to explain the film after viewing it (which is trickier that it will seem at first), you may realize that the real brilliance of this film is in the levels of its narrative. At its core, it is a basic psychological thriller. Simultaneously, and perhaps subconsciously, it also meditates on weighty issues of reality and identity- consider what the imperative "Stay" means to different characters at different points in the film, and it's almost like you're watching an entirely different movie than you originally thought.
Finally, the visuals in this movie provide their own context and narrative regarding the fragile nature of human memory and perception. This is the best looking movie I've seen in a long time, and the fact that it's combined with such a great story and cast makes this a rare treat.
If there is a weak link here, it's probably Gosling, who I think missed some opportunities to really dig in with his character and creep us out. Still his acting is better than that of most of Hollywood's garbage these days.
Final verdict: if you want a smart and unsettling film that will spur a serious discussion, watch this. You won't be disappointed.
