In 1874, Clint Wallace and his foreman, Ben Thompson, are driving their cattle from Texas to Wichita, Kansas, the new trail head of the West, when they meet lone rider Wyatt Earp. The taciturn Wyatt relates that he wants to start a business in Wichita, to which the railroad has just come, and rejects Wallace's job offer. Late at night, Gyp and Hal Clements, two of Wallace's cowhands, steal Wyatt's money, but Wyatt surprises them and retrieves his cash. Thompson, afraid that the quick-drawing Wyatt will shoot the Clementses, pulls a gun on him to make him drop his weapon, and Wyatt then thrashes Gyp in a bare-knuckles fight. Wyatt rides off and soon reaches Wichita, which is bustling with preparations for the arrival of Wallace's many cowhands, who the town hopes will be the first of many. Unable to find a place to stable his horse, Wyatt seeks advice from newspaper publisher Arthur Whiteside, who takes an immediate liking to the stranger when he professes an aversion to saloons and violence. Wyatt accompanies eager reporter Bat Masterson to a ceremony welcoming the railroad to Wichita, at which businessman Sam McCoy, the man largely responsible for the venture, speaks. Wyatt then goes to open a bank account but is interrupted by a gang attempting to rob the bank. While Bat protects Sam's daughter Laurie, who is also present, Wyatt foils the robbery and is asked by Mayor Andrew Hope to become the town's marshal. Wyatt demurs, stating that he is a businessman, not a lawman, but Sam, believing that Wyatt's actions belie his words, advises Hope to ask Wyatt again. Later, Hope and Whiteside speculate about Wyatt's past, which includes a term as marshal of a town overrun by crime. Wyatt had cleaned up the other town after its marshal, Billy Smith, the current marshal of Wichita, was chased out. The next day, the town leaders greet the just-arrived Wallace and Thompson, while the cowhands head for the saloons and dance-hall girls. Wyatt runs across Laurie and escorts her home, cautioning her not to go out alone until after the cowboys depart. As time progresses, the cowboys become drunk and raucous, and soon, led by Thompson and Gyp, begin galloping through the streets and shooting into the air. During the "hurrah," as the unruliness is called, a saloon girl is injured and a toddler, fascinated by the noise, is killed as he stands in front of a window. Infuriated, Wyatt demands Billy's badge and a shotgun, and heads into the street alone. Wyatt forcefully tells the culprits to drop their weapons, and although Gyp initially refuses, Thompson realizes that Wyatt will shoot them if they do not comply. Wyatt jails the drunken men, then, knowing that he will be unable to get them convicted of murder, tells Hope that he will make the men leave town. Hope, fearing the loss of the men's business, worries that Wyatt's solution is too drastic. The next morning, Wallace asks Wyatt how much the men's fines will be, and threatens a jail break when Wyatt informs him that he will have to wait until after the trial before his men can be freed. Wyatt promptly arrests Wallace, and although Sam applauds Wyatt's firm handling of the situation, he warns the new marshal that Wichita's prosperity depends upon the cattlemen. Wyatt retorts that he will not stand by while children are murdered, then forces the offenders to leave town. Afterward, Wyatt institutes a ban on firearms within city limits and allows the admiring Bat to act as his deputy until the reinforcements he has sent for arrive. The town leaders, including Sam and saloon owner Doc Black, complain to Hope that Wyatt has gone too far and decide to confront him. At dinner that night at the McCoys, Wyatt and Laurie flirt and plan on picnicking the following day. After dinner, Wyatt grimly tells the men that he will not change his methods of combating violence, and that if they are not satisfied, they will have to fire him. Before they can reply, news comes that some of the errant cowboys have returned to Wichita, and Wyatt goes after them. Wyatt gets the drop on the troublemakers in a saloon, and warns them that if they return, he will not waste time arresting them, but will kill them instead. Later, while Wyatt and Laurie picnic, he professes his feelings for her, stating that he does not want to waste time with demure courting, and Laurie responds with a kiss. In the evening, two gun-toting strangers arrive in town, and Black, assuming that they are the gunslingers he summoned from Wallace's ranch, hires them to kill Wyatt. While the men are laying their plans, Wyatt takes Laurie home, and there, Sam, worried that Laurie could get hurt if an outlaw comes gunning for Wyatt, asks him not to see her again. Wyatt reluctantly agrees, then goes to Black's saloon, where Black is mortified to learn that the two strangers are Wyatt's brothers, Morgan and Jim. An infuriated Black vows vengeance as he is forced to leave town, then meets with Clements and his cohort Al. Meanwhile, Laurie seeks out Wyatt, and he explains why her father has prohibited their relationship. He walks her home and there is confronted by Sam and Hope. Much to Sam's surprise, Hope supports Wyatt's law-and-order methods and refuses to fire him. After the men quarrel, Wyatt leaves but is shot at by Black, Clements and Al. Mary, Sam's wife, is hit by a stray bullet and killed instantly. Accompanied by his brothers, Bat and Whiteside, Wyatt pursues the killers and succeeds in shooting Clements and Al. Black escapes and travels to the Wallace ranch, where he incites the men by lying about Wyatt's actions. Believing that Wyatt killed his brother in cold-blood, Gyp heads a group of men riding to Wichita, but upon their arrival, the men learn the truth about Mary's murder. Sam, who now regrets his harsh words against Wyatt, stands beside the marshal as he faces the men. When Gyp insists on a duel, Wyatt outdraws and kills him. Black then attempts to shoot Wyatt, but Sam shoots him first. As the rest of Wallace's men leave, Sam and Wyatt shake hands, and soon after, Laurie and Wyatt are married. While watching the bride and groom wave goodbye, Sam shakes his head, telling Whiteside that he tried to persuade Wyatt not to leave Wichita for a new job as marshal of Dodge City.
