Possessor

Colin Tate: Just think, one day your wife is cleaning the cat litter and she gets a worm in her, and that worm ends up in her brain. The next thing that happens is she gets an idea in there, too. And it's hard to say whether that idea is really hers or it's just the worm. And it makes her do certain things. Predator things. Eventually, you realize that she isn't the same person anymore. She's not the person that she used to be. It's gotta make you wonder, whether you're really married to her... or married to the worm.