We all have that side to us. The side filled with rage and anger. Some of us can seen it much more clearly while others need to be taken to the height of their anger for that rage to be released. Some can't control this rage when it gets to this point. The results can make a mentally unstable person delusional.
This is what plays out in this film. A man with so much obsession that he couldn't control his actions. It was his unconscious mind that took him over. His guilt, jealousy, and denial are what forces him to do the terrible things he does. He won't stop until he's tricked his conscience!
Unseen will have you always guessing what he has done and what he will do next!