Ed Bailey and his two henchmen ride into the small Texas town of Fort Griffin, hoping to avenge the death of Bailey's brother at the hands of noted gunslinger John H. "Doc" Holliday. Holliday's traveling companion, Kate Fisher, rushes to warn the former dentist at his hotel room, but the two instead come to blows when Kate inadvertently mentions Holliday's once-prominent family. Meanwhile, lawman Wyatt Earp arrives in Fort Griffin, and learns that Cotton Wilson, the town's cowardly marshal, released outlaws Ike Clanton and Johnny Ringo from custody three days earlier, despite the outstanding warrants for their arrest. Seeking information on Clanton and Ringo's whereabouts, Wyatt questions Holliday, who refuses to tell the lawman where the outlaws went, as he carries a grudge against the Wyatt family because Wyatt's brother Morgan once threw Holliday out of Deadwood and impounded $10,000 of his gambling winnings. Soon thereafter, Holliday confronts Bailey and challenges him to a gunfight at Boot Hill, but when Bailey attempts to shoot him in the back instead, Holliday throws his knife and kills the cowboy. Arrested for murder, Holliday is saved from a lynch mob by Wyatt, who, along with Kate, helps the gunfighter escape the angry townspeople. Later, back in Dodge City, Kansas, Wyatt is told by his deputy, Charles Bassett, that Holliday and Kate have arrived in town. Wyatt orders the gunfighter to leave, but when Holliday informs him that he is penniless, the lawman allows him to stay if he promises not to cause any trouble. Wyatt's attention is then drawn to another new arrival in Dodge City, the beautiful Laura Denbow. After being told by Wyatt that female gamblers are not allowed within the city limits, Laura is arrested for "disturbing the peace" after a drunken cowboy attempts to come to her defense. Under pressure from Holliday and Bassett, Wyatt has a change of heart and releases Laura, on the condition that she confine her gambling to the saloons' side rooms. Later, Wyatt is forced to deputize Holliday when a local bank is robbed and its cashier killed, as all his deputies are out on a posse with Bat Masterson. As they set up camp for the night, Holliday tells Wyatt that he agreed to come along only to repay his debt to the lawman for saving his life back in Fort Griffith. His opportunity soon arises when the three bank robbers attempt to ambush Wyatt, but are instead killed by the two men. Returning to Dodge City, Holliday learns from Bassett that Kate has left him for Ringo. Despite his anger and injured pride, Holliday keeps his promise to Wyatt and refuses to get into a gunfight with Ringo. Unlike his new friend, Wyatt's love life is on an upswing, as he and Laura soon fall in love. With Wyatt out of town with his new lady love, cattleman Shanghai Pierce rides into Dodge City with his cowboys and begins shooting up the town. When Bassett tries to arrest Pierce, Ringo shoots him. Wyatt then returns to town just as Pierce and his men are breaking up a church bazaar. Outgunned, Wyatt is saved when a well-armed Holliday appears from a back room, and Pierce and his men are quickly arrested. Afterward, Wyatt tells Holliday that he is giving up the law and moving to California with Laura, despite being offered the post of U.S. Marshal. Wyatt then receives a telegram from his brother Virgil, asking for his help in cleaning up the town of Tombstone. Though Laura refuses to go, Wyatt immediately leaves for Arizona, with Holliday following close behind. At Virgil's home, Wyatt is joined by two other brothers: Morgan and James. Virgil tells them that Ike Clanton has rustled thousands of heads of Mexican cattle, but cannot ship them to market as long as the Earps control Tombstone's railway station. All agree that Wyatt should be in charge of the situation, though Morgan criticizes his older brother's association with Holliday. Wyatt, in turn, defends Holliday and insists that the gambler remains welcome in Tombstone as long as he stays out of trouble. Cotton, the new county sheriff, offers Wyatt a $20,000 bribe from Ike if he allows the Clantons to ship their stolen cattle. Refused, Ike and his men then ride into Tombstone, only to be turned away by the Earp brothers. Later, Ringo returns to town with Kate, and Holliday quickly challenges him to a duel, but is stopped by Virgil. Meanwhile, Wyatt heads out to the Clanton ranch to inform Ike that he has been made U.S. Marshal for the territory and orders the crooked cattleman to take his stolen herd back to Mexico. Unable to find any legal loopholes around Wyatt, the Clantons decide to ambush the lawman while he makes his rounds that night, but they mistakenly kill James instead. While questioning Kate about James's murder, Holliday collapses from an attack of tuberculosis. That night, Billy, the youngest Clanton, is sent into town to challenge the Earps to a family duel. Outgunned six to three, Wyatt asks Holliday for help, only to be told by Kate that the bedridden gunfighter is dying. The next morning, Ike, Finn and Billy Clanton, along with Tom and Frank McLowery and Ringo, head into Tombstone to face the Earps. Despite his illness, Holliday joins the Earps as they head for the O.K. corral. The gun battle begins, and Morgan is quickly wounded. In turn, Holliday shoots and kills Finn. His death is quickly followed by that of the two McLowerys. After Virgil is wounded, Wyatt kills Ike with a shotgun blast. Though wounded by Billy, Holliday follows Ringo into a barn and kills him, while Wyatt chases after the youngest Clanton. Billy is then offered a chance to surrender, but he refuses and is killed by Holliday when Wyatt hesitates to shoot the young man. Afterward, while his brothers tend to their wounds, Wyatt joins Holliday for a final drink before heading off to California, and hopefully, a waiting Laura.
