At 10:30 on a quiet morning in 1870, three outlaws ride into the western town of Hadleyville just as its marshal, Will Kane, is being married to a pretty Quaker named Amy Fowler. To please Amy, Will resigns his post immediately after the ceremony, but he is troubled because the new marshal has not arrived to take his place. Suddenly the station master rushes in with the terrible news that Frank Miller, a wild outlaw whom Will had arrested for murder five years earlier, recently received a pardon and is due to arrive in Hadleyville on the noon train. The three outlaws, Jack Colby, Ben Miller and James Pierce, have ridden to the station and are awaiting Miller's arrival. Alarmed, the wedding guests urge Will and Amy to leave town immediately, but after only a few moments on the road, Will turns the wagon around and heads back. "I expect he'll come looking for me," Will replies when Amy asks for an explanation. Will's young wife begs him to leave with her, and when he protests that he has never run from anyone, she threatens to leave on the train whether or not he accompanies her. Will hurriedly begins to make plans for the town's defense, and is surprised when Judge Percy Mettrick, who had sentenced Miller to be hanged, packs his belongings and flees. Will is relieved to see Harvey Pell, his deputy, still in town, but Harvey, angry that an outsider was hired to replace the retiring marshal, agrees to stay only if Will promises to support his bid for the post. Will refuses, whereupon Harvey removes his guns and walks out. Will visits his old flame, businesswoman Helen Ramirez, who had formerly been Miller's mistress. Will warns Helen about Frank, and she admits that she has sold her store and plans to depart on the noon train. In the saloon, men who enjoyed the rowdy times when Frank and his henchmen controlled the town celebrate his imminent return and refuse Will's request for help. Will then visits the home of his friend, Sam Fuller, but as Sam listens from the next room, his wife tells Will that he is not at home. Next, Will interrupts the church service to ask for deputies. Although several of the townspeople proclaim that it is Will who has made their town safe and decent, many of them also argue that Miller's impending arrival is not their problem. Finally, Mayor Jonas Henderson declares that a gunfight would hurt the town's image and that Will should have left when he had the chance. Stunned, Will leaves the church and asks his mentor, Martin Howe, for help. Howe, once the marshal himself, has become cynical, however, and after Will exits his home, he mumbles, "It's all for nothing, Will." Harvey, now drunk, tries to force Will to leave town, but Will refuses, and the two men fight until the marshal knocks his former deputy unconscious. As noon approaches, Amy visits Helen, who assures her that there is no longer anything between herself and Will. She also reproaches the young wife for not defending her husband, but softens after Amy reveals that both her father and brother were killed in a gunfight. In Will's office, the only citizen who had willingly pinned on a deputy's badge now backs out and goes home, leaving the marshal utterly alone. Will writes his last will and testament, then enters the deserted street as Amy and Helen drive a wagon toward the train station. The train arrives, and as Miller disembarks, the two women get on board. Miller straps on his gun, and the four outlaws walk toward the center of town, where Will awaits them. When one of the outlaws breaks a window, Will is able to duck inside a building and shoot him. Hearing the shot, Amy gets off the train and runs back to town. Will kills another of his attackers and takes cover in the livery stable, which the two remaining outlaws set on fire. As the frightened horses charge out, Will leaps on one and makes his escape, but falls after being shot in the arm. Amy shoots one of the gunmen in the back before he can shoot Will, but is captured by Miller, who uses her as a hostage. In response to Miller's threats, Will faces him in the street, but Amy pushes the outlaw, giving Will the chance to shoot him dead. Amy and Will embrace, and the townspeople rush into the street. Disgusted by the cowardice of his former friends, Will tosses his tin star in the dirt at their feet, then leaves with Amy.