The Pledge
Starring Jack Nicholson & directed by Sean Penn, it's about a retired cop who, following the brutal murder of a young girl, becomes utterly consumed in his obsession with finding what he believes to be the true culprit.
I really enjoyed it (but then I tend to enjoy anything that has Sean Penn's name attached) due in large part to Nicholson's central performance. I think this is mainly because it's one of the first films in which he acknowledges his advancing years in real life, & the portrayal of a man whose days are in a sense numbered, is all the better for it. He lends an urgency to his characters obsession that few other actors could pull off.