I'm teaching the Cortazar short story "House Taken Over" in summer school, and I want to show a movie that is somehow related to it. The story has a fantastical element - there is something that takes over the house where the protagonists live, but that something or somebody is never seen or explained. Is there a good, or good enough, horror movie that has a similar theme? Even if the "monster" was revealed eventually, is there a movie where for long periods of time, the monster was left up to the imagination? And will I get fired for showing it to high school kids? Thanks for the help.