Plot
Former sea captain James McKay travels to the American West to join his fiancée Patricia at the enormous ranch owned by her father, Henry "the Major" Terrill. After a meeting with Patricia's friend, schoolteacher Julie Maragon, McKay and Patricia are accosted by a group of drunks led by Buck Hannassey, the son of the Major's ardent and implacable enemy, Rufus Hannassey − with whom he has had a longstanding feud over water access for cattle. In spite of the harassment and mockery, McKay surprises Patricia by making light of the incident, and stating that he has experienced worse and the boys meant no harm; they were just drunk.
The next morning, McKay declines an invitation from the Major's foreman Steve Leech to ride an indomitable bronco stallion named "Old Thunder". McKay then brings a pair of dueling pistols once owned by his father to the Major as a gift. When the Major learns of Buck's pestering of his daughter and future son-in-law, he gathers his men and goes to raid the Hannassey ranch, despite McKay's attempts to defuse the situation. The Major's group of 20 men finds neither Rufus nor Buck, so they settle for terrorizing the Hannassey women and children, shooting holes in the Hannassey water reservoir. They find Buck's posse in town and proceed to beat and humiliate three of them. Meanwhile, McKay privately tames and rides Old Thunder after many unsuccessful attempts, and swears his only witness, the ranch hand Ramon, to secrecy.
A gala is held on the Terrill ranch in honor of Patricia's upcoming wedding. At the height of the festivities, an armed Rufus crashes the party and accuses the Major of the hypocrisy of pretending to be a gentleman when his actions speak otherwise. The next day, McKay secretly goes to Julie Maragon's abandoned ranch, known as the "Big Muddy", the property at the center of the Terrill-Hannassey dispute. With the only river nearby running through it, access is vital for both herds during times of drought. McKay persuades Julie Maragon to sell the ranch to him in the hopes of both securing a gift for Patricia and ending the conflict by continuing Maragon's policy of unrestricted access to the river. McKay shows up at the camp of the Terrill search party, led by Leech, sent out to find the presumed-lost McKay.
Upon returning to Ladder Ranch, Leech calls McKay a liar when McKay explains he was never lost or in danger. Again, McKay refuses to be goaded into a fight, which disappoints Patricia enough to make the pair reconsider their engagement. Before dawn and without an audience, McKay challenges Leech to an outdoor fistfight. The prolonged fight ends in a draw. In the morning, Maragon tells Patricia of McKay's purchase of the Big Muddy as a wedding gift for her, which initially convinces her to attempt to make amends with McKay. When she learns of McKay's plan to allow the Hannasseys equal access to the water, she leaves for good.
Wanting to lure the Major into an ambush in the canyon leading to his homestead, Rufus takes Maragon hostage. Although McKay personally promises Rufus equal access to the water, he finds himself in a clash with Buck, which is ultimately settled with a shootout using the old dueling pistols. Buck fires before the signal, his bullet grazing McKay's forehead − and leaving him open to be shot by McKay. Buck crawls under a wagon in a display of cowardice that convinces McKay to spare him. The frustrated Buck snatches another gun from a nearby cowboy, forcing Rufus to kill his own son. Rufus then goes to the canyon for a final confrontation with the Major and challenges him to a one-on-one showdown. Armed with rifles, the two old men advance and kill one another.
With that, the hostilities end, and McKay and Julie, clearly falling in love, ride off together with Ramon to start a new life together.
