Headstrong Thomas Dunson starts a thriving Texas cattle ranch with the help of his faithful trail hand, Groot, and his protégé, Matthew Garth, an orphan Dunson took under his wing when Matt was a boy. In need of money following the Civil War, Dunson and Matt lead a cattle drive to Missouri, where they will get a better price than locally, but the crotchety older man and his willful young partner begin to butt heads on the exhausting journey.

An aging group of outlaws look for one last big score as the "traditional" American West is disappearing around them.

约翰·达顿是达顿家族的一家之长，坐拥着美国最大的牧场，与牧场毗邻的有美国首个国家公园、印第安人保留地以及土地开发商买下的地皮。在一次因牲畜误入印第安人保留地引起的争端中，不幸的意外伤亡事件发生，一场涉及多方的争端在蒙大拿州这片美丽的土地上拉开了序幕。