It's the 1880s and Boss Spearman (ROBERT DUVALL) and Charley Waite (KEVIN COSTNER) have been fellow cattlemen for nearly a decade and are currently moving their cattle and horse herds with the help of Mose Harrison (ABRAHAM BENRUBI) and 16-year-old Button (DIEGO LUNA). Without any land they call their own, they move throughout the open range, allowing their livestock to graze in vacant fields.
That doesn't sit well with Denton Baxter (MICHAEL GAMBON), an Irish immigrant who runs a small town with the aid of his hired gunslinger Butler (KIM COATES) and the local law, Sheriff Poole (JAMES RUSSO). When Mose doesn't return from their town after heading there for supplies, Boss and Charley discover that he's been jailed and beaten by Baxter's men. With the medical aid of Doc (DEAN McDERMOTT) and Sue Barlow (ANNETTE BENING), they patch up Mose and leave town, but have no intentions of backing down.
It gets worse when they realize that the locals intend to either take or disperse their herds. Just as they confront a bunch of Baxter's thugs, others severely wound Button and kill Moses and their dog. After leaving Button with Sue, the two cattlemen - with the aid of a few locals including old timer Percy (MICHAEL JETER) - set out to get their revenge on those who've wronged them.