Siblings Sam (Tobey Maguire) and Tommy Cahill (Jake Gyllenhaal) are as far apart as brothers can be; while Sam serves his country as a Marine, Tommy is a drifter who just got out of prison. When Sam is shot down and presumed dead in Afghanistan, Tommy vows to take care of Sam's wife, Grace (Natalie Portman), and his children. Tommy and Grace become close, and when Sam unexpectedly returns home, the consequences of their actions threaten the foundation of the entire family.
