When a shady-looking stranger rides into town to join his old friend it is assumed he is a hired gun. But as the new man comes to realise the unlawful nature of his buddy's business and the way the homesteaders are being used, the two men draw apart to become sworn enemies.

This western begins with St. Louis resident Lutie Cameron (Katharine Hepburn) marrying New Mexico cattleman Col. James B. 'Jim' Brewton (Spencer Tracy) after a short courtship. When she arrives in "Salt Fork, NM" she finds that her new husband is considered by the locals to be a tyrant who uses force to keep homesteaders off the government owned land he uses for grazing his cattle--the so-called Sea of Grass. Lutie, has difficulty reconciling her husband's beliefs and passions with her own.