Interesting.
Good story, and fantastic use of suspense. I really like where this story is going. However, I must say that I dislike your animating style. Your animation itself is pretty fluid and decent enough when it comes to non-characters, and the opening scene in particular is incredible.
What I find difficult to handle, though, is that your characters are "cartoon" while most everything else is "real." If this was something light on story, such as a stick figure battle or the like, then it would be negligible, but not with an animation like this. When you're developing characters, trying to make them seem like actual people, it is very important to make them seem as lifelike as they can be. It needs to be as easy as possible to relate to the characters, and that means having them look, talk, act, and move realistically. Your characters, unfortunately, constantly remind me that I'm watching a cartoon. In the sequel, I strongly suggest that you make more detailed and fluid characters. Such devotion to everything else is amazing; just apply youself as much to your characters.