It's with Casey Affleck as this private investigator who usually just finds people who disappear on purpose and is hired by the frantic aunt of this four (three?) year old girl that goes missing. The family is really poor and the girl's mom is a druggie. Morgan Freeman is also in it as a cop who lost his own daughter about twenty years before. She was murdered, so he feels pretty strongly about this case.
You should see it, really. It's not a cop drama. It's more about Casey's character's own demons, especially at the end, when he's trying to do what he knows is right but not necessarily right. (If that makes any sense. It will, if you watch it.)
But it's a really deep movie, might stay with you for a few days, that I truly enjoyed.