This is more scary than horror movies
I didn't know much about this before watching it. That's usually the best way to go into a film but it's hard to avoid details most of the time.
I was feeling dreadful most of the time. This movie had a subtle menacing tone and kept me glued.
I think this was more frightening than movies about slashers or ghosts or zombies. This is a situation that happens in real life, and anyone with dumb teenager kids (especially daughters) can find what's scary in this.