We're first introduced to a trio of men led by Ketchum (Stephen Dorff) pursuing and brutally extracting information from another man. We then meet Henry (Tim Blake Nelson) and his son Wyatt (Gavin Lewis), working hard to maintain a life on their farm - a life Wyatt is very unenthusiastic about. Henry finds a badly injured man who's been shot, and a very large amount of cash. He reluctantly takes the man home to get him a doctor, which puts him on a collision course with Ketchum. Most people - particularly Wyatt - assume Henry is "just a farmer," but we know better and Ketchum spots it immediately.
Blake Nelson has always been a decent actor, although he's generally leaned to fairly comedic roles. This role isn't remotely comedic. Henry has a terrible haircut and a droopy eye and he really doesn't give a shit how he looks, he's a farmer. He's also far, far more dangerous than he initially appears. This is the performance of Blake Nelson's life (so far): he's excellent. The story is brutal, dark, and very effective.
It's also very similar - in my mind - to Clint Eastwood's "Unforgiven." Both are about older outlaws who have settled down to domesticity but are forced to revive the skills of their youth. Eastwood's character embarked on that voyage slightly more voluntarily, but neither story ends well. This one stands on its own though: it's a very fine piece of work.