There are a few scattered scenes of violence in this film that keep it from a PG rating. One involves a person being brutally stabbed twice with a knife, and there is some blood. The most intense part about this scene is that the character being stabbed is a very likable character and the stabbing is very unexpected. This will probably bother most people quite a bit. It shocked me when I first saw it, and I was fifteen at the time. That said, though parts of this film are intense and scary, there's really not a lot to worry about in the way of content. There is no sex at all. No dialogue. No nudity. No steamy sexual encounters (unless you count some brief kissing which is handled sweetly and innocently). There is no language either. A few people say, "Oh, God!" twice. But they are religious people and they are not cursing.
This is not one of M. Night Shymalayan's most popular films, but I thought that it was very good. Bryce Dallas Howard, Joaquin Phoenix, and Adrien Brody are phenomenal! I loved the sweet romance, the chill that ran down my spine in a few scenes, the haunting beauty of the film, and the positive messages that fill it.
I'm nineteen years old and this is one of my favorite movies. If you have kids, you might let some of them younger than thirteen see it, if you are willing to fast-forward the one or two violent scenes. It still might be too scary for more sensitive children, but overall not as dark as one might expect.