The Hatfield-McCoy feud heats up when one family's daughter elopes with the other's son.

Toward the end of the nineteenth century, in the Kentucky hills, Old Randall McCoy reminds his sons, Tolbert and Little Randall, about their long-standing enmity with the Hatfields, a coarse, impoverished clan that lives across the Big Sandy river in West Virginia. Later, at the country fair, Old Randall's daughter Roseanna is picking flowers for a picnic table when she is stung by a hornet, and handsome Johnse Hatfield comes to her aid. As soon as she finds out who he is, she reviles his clan for having shot and injured her mother years before. Johnse protests that his kinsman Mounts, who fired the shot, is half mad, but Roseanna leaves in anger. That evening, during the square-dancing, Johnse takes Roseanna aside and tells her that she will be his, then kisses her, unaware that Little Randall is watching from the bushes. Roseanna is entranced by Johnse, and when her beau, shopkeeper Thad Wilkins, proposes to her several days later, she sadly tells him she can never marry him because she is "bad." Later that night, a sleepless Roseanna goes outside and finds Johnse waiting for her. He carries her across the river on his horse and introduces her to his parents, Devil Anse and Levisa, as his future bride. Although Anse objects to their marriage, he warms to the idea of renewing hostilities with the McCoys, and he and his older sons, Ellison and Cap, head to the old fort to prepare for battle. Johnse goes in search of a preacher to perform the marriage, leaving Roseanna with his mother, and the two women begin to forge a relationship. That evening, word arrives that Cap has been crippled in an accident at the fort. While Anse and Levisa are tending to their son at the fort, the psychotic Mounts, who has bitter memories of his own father's death at the hands of the McCoys, slips away and goes to Anse's cabin. He menaces Roseanna with a knife, but Anse, who has followed Mounts, rescues her. Johnse returns later and says he was unable to find the preacher. The next day, Roseanna is getting water when Little Randall, having guessed her whereabouts, approaches her, and she agrees to go home with him. She bids Johnse goodbye, making plans for him to call on her father the following night. The next evening, on his way to meet the McCoys, Johnse stops at Thad's general store while Tolbert and Little Randall are shopping there with their older brother Phamer. The Hatfield men enter, and Mounts starts a brawl. When Little Randall attempts to defend his uncle with a knife, Mounts shoots him, and the fight quickly escalates into a shootout. Meanwhile, Roseanna has just convinced her father to talk with Johnse when Thad comes to the door with the wounded Tolbert and reports that Little Randall has been hurt and is trapped in the store with the Hatfields. Roseanna follows her father and Thad to the store, and after ordering his kinsmen to hold their fire, Johnse lets her in. Mounts then uses Roseanna, Johnse and Little Randall as shields to escape, and Randall declares all-out war against the Hatfields. During the fighting at the fort, Johnse sneaks out to meet Roseanna. Mounts follows them and is about to shoot the lovers, but Johnse shoots and injures him. Roseanna and Johnse then mount her horse, planning to ride to find the preacher, and when Mounts prepares to fire at them, Anse shoots and kills him. Both sides then stop shooting, and everyone watches as Johnse and Roseanna ride off together.