Some explain what happened? Spoilers requested.

I think I did not really get the twist in the end. The way I understand it, "Isis" was the main characters wife, but he hallucinated her to be the woman in the epiloque which he lost years ago. During the party, he sees her as the blonde woman, while his guests see her as a brunette called Isis. Now how does this come together with his friend entering the house wearing a mask (is he just drunk and stupid)? What about these "premonitions" - they are not really explainable by him beeing crazy, are they?
Maybe I don't get the movie because I don't speak english as a native language, or maybe the movie was just bad as other people here suggested?

Maybe someone can explain??