Nice story-line and performances but a disappointing ending

Rating: 4/10 (1 January 2017)

First of all, I should start this review by stating that I was very excited to see this film. I rarely go to the cinema and this was one of the films I had picked out to see at the cinema which means I liked it very much.
Secondly, the performances were brilliant which was an important aspect of this film since it featured only a few actors which were also the protagonists. Its claustrophobic theme was breathtaking: you were feeling for the 3 people and could sympathize with all 3 of them, even though you didn't know if they were actually nice or disturbed.
The film was indeed a roller-coaster ride. You were led to believe that the ''abductor'' was a kind guy who just wanted to help, then you find out that he has probably abducted other women and killed them so he must be crazy and then, the twist at the end informs you that you should have believed him and that he didn't want to hurt you (as much) after all.
But, I rated this film with 4 out of 10 stars because the ending, although I did not expect it, involved aliens which made the film sci-fi, which was not the reason I wanted to watch it. On the contrary, I was expecting another genre and I didn't like that kind of transformation. Plus, the aliens that seemed to be very powerful at first, eventually retreat when the female protagonist -in the heat of the moment, tired, shocked and scared- attacks them with what? A bottle?
In conclusion, the ending came of as sketchy and sloppy, as if they had wasted the film's minutes building up the suspense and then they ran out of time, so they just surprised us with some aliens and a very cheap solution so that the female protagonist can survive.