Just watched this after it popped up on Netflix. The concept is great and the tradgedy and what ensues kept me invested throughout the entire film. I'm unsure how the two major tradegies tie together in a clear way as the brief description states. My advice is to ignore and preconceptions and just watch the film without expecting anything.
My biggest criticism is the mixing of the two storylines and how the main characters aren't fleshed out enough to give clear indications of exactly what's going on. I expected a twist ending as it seemed obvious that whoever was responsibile for Katie likely didn't have anything to do with the main characters.
Regardless of any criticisms I would defintely recommend this film. I'm more than satisfied using my time to engage in this film.