In 1876, cowboy Lin McAdam and his good friend, Frankie "High Spade" Wilson, travel to Dodge City, Kansas to participate in the Centennial Rifle Shoot, which is being held on the Fourth of July.  Lin knows that his sharp shooting brother, Dutch Henry Brown, whom he suspects murdered their father, will also be in the contest, as first prize is a rare Winchester '73 rifle.

Soon after their mutual arrivals in Dodge City, Lin and Dutch Henry are stopped from killing each other by the town's famous marshal, Wyatt Earp.

Later, Lin narrowly defeats his brother in the rifle contest, but Dutch Henry and his friends ambush Lin and steal the Winchester.  Two days later, a penniless Dutch Henry loses the rifle in a poker game to Joe Lamont, an Indian trader.  Lamont is later killed by Young Bull, an Indian chief whom Lamont had hoped to cheat with defective guns and rifles.

Meanwhile, Lin learns from Jack Riker, a saloon keeper, that Dutch Henry is headed for Tascosa to meet up with Waco Johnny Dean, an outlaw.  That night on the trail, Lin and High Spade run into a U.S. Cavalry unit, led by Sergeant Wilkes, which has been surrounded by Young Bull's warriors.  The Indians attack the next morning, but they are repelled when Lin shoots and kills Young Bull.  After Lin and High Spade leave, Wilkes discovers the rare Winchester by the dead Indian chief and gives it to Steve Miller, the cowardly fiancée of Lola Manners, a dance hall girl.

Steve and Lola then travel to Tascosa, where they accept the hospitality of the Jameson family.  Waco Johnny and his men soon arrive at the Jameson home, with a posse in hot pursuit, and the outlaw uses Lola as a hostage when Steve refuses to give him the Winchester.  Waco Johnny kills Steve in a gunfight, then escapes from the farmhouse with Lola and the rifle and heads for Dutch Henry's hideout in the nearby mountains.  Dutch Henry quickly recognizes the Winchester and demands it back.

The outlaws then plan a bank robbery, only to have Lin and High Spade arrive in Tascosa that same day.  Lin kills Waco Johnny just as Dutch Henry and his men are leaving the bank, and Lola is shot and wounded in the ensuing gunfight.  Lin takes off alone after his brother, who heads back toward his mountain hideout.  Though he is trapped below Dutch Henry, Lin torments his brother by calling him by his given name, Matthew McAdam, then manages to sneak behind him as he reloads the Winchester.  Lin then shoots and kills Dutch Henry, finally avenging their father's death.

Later, Lin returns to Tascosa with the Winchester, where his return is welcomed with open arms by both Lola and High Spade.