You don't watch this movie expecting something, you watch Jess Franco.
There are numerous variants of Spanish original--I prefer the one with English subs. The high point of this flick is not movie but some music and picture before anything start and when I see and listen I tell myself--this freaking guy is genius and I'm moron and its self-obvious. The flick itself is very simple and not much plot involved and it looks almost lousy if not for hot chicks and soft porn concentration.
