Nicole Kidman has played troubled women quite a few times before, but the performance she gives here is quite fresh, and really unlike anything I've seen before, either from her or anyone else. The character she plays is also quite thoroughly developed, and my shitty memory says she is the greatest female asshole I've seen yet in any movie. This character is grieving of son's accidental death.
The guy playing the killer gives the movie's best performance, and perhaps the best teenage performance in any movie (remember the quality of my memory). He's fucking amazing. And this is a movie not having any shortage of excellent acting. Most notably, we have Sandra Oh, who is as desirable as she is excellent. She is a good actor, but she hasn't in my eyes done anything better than this.
I'm still not sure about Aaron Eckhart. Not a bad performance at all, but he's too uninteresting. I'm also not sure about the lady playing the mother. Not bad either, but not too believable.
The dialog is quite good and so is the camerawork. The great direction easily hides the fact the movie itself is pretty much plotless.