A brilliant concept, clearly inspired by The Game thriller and Saw series of horror movies. I am a fan of Ron Perlman, so long as he's not given shit roles like in Pacific Rim. He does great work here, him and Rutina Wesley. The 'happy' ending thing is also stupid. The voice acting of the evil guy on the phone is wonderful, and so is his script. What a pleasure!
Story concepts this good seldom have great conclusions, and this one is no exception. The twist is just not needed at all (it's too much of a stretch, both the father and brother thing). It would have also been nice to have more of a reveal of the villains.