First, it's nothing like the blurb. I'm thinking there was some demon or ghost that haunted this apartment that prevents these people from escaping.
However, I can only conclude these were three people with mental issues in the first place who became stuck in this apartment due to some technical malfunction of the building, or some nut doing the "Human Experiment Project". What happens is it caused the paranoia to kick in or it was some drug induced psychosis which brings out their inner fears and or psychotic disorders.
For instance if you were abuse as a child and pushed it out of your mind as an adult it manifest in flash backs and attacks of crippling terror. That's what a lot of this film felt like. It's like flashes of your worst personal nightmare. Such as...you are a heartless sexual sadist who hid behind a mask of wholesome goodness then you find yourself in a situation you can't hide your afflictions and you give in to your basic animal urges.
All I know about this film is I needed to be smoking whatever all those who left these raving reviews were smoking.
Honestly, peeps, this is another one of those films that is all about shock value and an attempt at avant-garde cinema. Good attempt; but this type of film has been done better and at the very least has left you thinking about it long afterwards. Not this puppy. You want to forget you stupidly sat there until the end, thinking if you keep watching it will make more sense at the end.
Okay, here goes my honest opinion, want it or not. This film would have been better off if it had been about vacationers fighting against a actual demon are ghost that wouldn't allow them to leave this apartment instead of this metaphorical mess. In my determination, they were only prisoners of their own minds.