This movie really doesn't sound like anything original but that however hardly is its biggest problem.
The movie is an absolutely mess to watch. It's never anything thrilling, scary, engaging or remotely interesting to watch, which is all really due to the fact that the movie is a difficult one to follow. And not because it has such a clever, original and tight script but just simply due to the extremely poor and messy story telling.
The trailer truly makes more sense than the actual movie. As a matter of fact, the trailer lets this movie seem like a pretty straightforward and formulaic possession movie but I wish that the actual movie itself was at least half as straightforward as its trailer. It just feels like some random scenes following one after the other instead, in which none of the different plot lines and different characters involved with it feel connected strongly- and effective enough to each other.
The movie is like a murder mystery disguised as a horror movie, or a horror movie disguised as a murder mystery, depending on how you look at it. It really feels like two completely different and unrelated scripts and ideas got put together but the two never blend in well with each other as well.
Maybe it still could have worked out as a good and interesting enough one, if only the characters were some better developed- and more likable ones. I absolutely never got the feeling that I ever got to know anything about any of the characters and the movie gave me absolutely no reason to ever care or root for any of them. The acting besides wasn't anything too solid either. Hard to say if this really was completely the actor's fault as well though. The script was most likely to blame for this as well.
Don't be deceived by the movie its good and professional look. It's really nothing but a confusing and messy to watch movie, that doesn't work out on any level.