'Dusk' is the kind of film that relies almost entirely on its ending to be considered a good film. It knows that it isn't made with the highest levels of quality, but it thinks that if its ending is good enough it might get away with that fact. There are after all a lot of examples of this in film history.
Unfortunately for 'Dusk' there are two problems in their case. Firstly, the film is very amateurishly made. The acting is quite terrible at times, the writing is bizarre in spots and structured painfully on occasion (mostly in the first 15 minutes) and the direction is bland and uncreative. So all this makes for not a very fun watch. However, because of the story line we know that something more is going on, something hopefully that will blow us away and make it all worth it. This is the only thing that keeps us from switching off the film altogether.
Then comes the second problem, the ending. While admittedly not bad, and while it does clear up a lot of points in the script that originally just seemed like very poor writing, it is unfortunately not enough to save 'Dusk'. You could say it saves it to an extent, but not to the levels I believe the film makers were looking for. The only people I could really recommend this to are absolute lovers of twists in films. Other than that you aren't going to get a whole lot out of this one.