À l'intérieur. Christ. Just... yes, À l'intérieur. Here be spoilers and seriously fucked up mental images.
So, this film is actually quite basic what horror movie plots are concerned. A pregnant woman looses her boyfriend in a car accident, and four months later, when she's quickly approaching the time to give birth, she starts getting stalked by a woman who seems... rather interested in her soon-to-be little bundle of joy. Her fascination manifests in the form of scissors, no points in guessing what she's going to use those for.
I'm a bit uncertain what to think of this movie. On one hand, it does what it's supposed to do hella good. I'm not quite certain what does so goddamn well, but the thought of a pregnant woman being put through The Strangers-levels of peril that just makes me uneasy. Not to mention that the whole "scissor C-section"-thing being teased from very early on, leaving that particular mental image to simmer in your mind until the end. Overall, the film is fairly similar to The Strangers, even though the body count is a good bit higher and the antagonist quite often is a bit more in the open.
My biggest complaint to the movie, though, is that the supporting cast, or cannon-fodder, as they end up being, are all fairly stupid. I mean, our villain du jour isn't some super-strong hillbillly, she's a fairly normal woman, her Audition-levels of The Crazy notwithstanding. When she manages to take out as many people as she does, most of them police officers, it does display some of that tried-and-true slasher movie stupidity. Granted, one of the most impressive things about this film is how it uses dramatic irony. More than once, our scissor-wielding psychopath manages to avoid capture by pretending either to be her intended victim or a relative of hers while our poor protagonist has barricaded herself in the bathroom, and although it gets old eventually, it is very suspenseful
A l'intérieur is a movie I'm a little bit ambivalent about recommending, partially because I find its imagery particularly disturbing, and also because it flips between tense physiologic horror and a sort of Slasher-type idiot plot that makes it sort of hard to take said imagery all that much more uncomfortable. Still, if you hanker for something profoundly fucked up and can't get yourself to see Irreversible, give it a shot