The trailer led me to expect an unusual psychological thriller & sadly I didn't do my homework in advance of renting. What we get instead is a sadistic derivative film that borrows much of its plot from Seven (a true masterpiece) & much of its sadism from "Hostel". There's no secret as to who the killer is - what is kept secret is how a slight young person manages to carry several huge men into compromising positions & where she developed the skills to build the torture apparatus. As for the twist- I saw it coming 20 minutes innto the film.
If you're after a good psychologic thriller rerent "Seven". Don't waste any time on this.
One of the best films I've seen great story line. Now I'm going to buy it ?? it reminded me of another great film the horseman of the apocalypse which is also about torture