On his wedding day a retiring marshal stays in town to encounter a released murderer but is unable to get any supporting deputies.
Ben Miller (Sheb Wooley), Jim Pierce (Robert Wilke), and Jack Colby (Lee Van Cleef) ride into town. Judge Percy Mettrick (Otto Kruger) weds Will Kane (Gary Cooper) and Amy (Grace Kelly), who is a Quaker. Will resigns as marshal but learns that Frank Miller was released, and that Frank’s brother is in town. Deputy Harvey Pell (Lloyd Bridges) sees Will leaving in a hurry. Will tells Amy that he has to go back. He tells her that he sent Miller up for murder and puts on his star. Amy begs Will to go and says she will take the train.
Judge Mettrick tells Will that he is leaving. Amy buys her ticket. Harvey tells Will that he wants to be marshal, but Will says he is not ready. Harvey thinks Will is jealous because he got Helen Ramirez (Katy Jurado). She laughs at Harvey and tells him to get out.
At eleven Amy waits in the hotel lobby for the noon train. Herb is Will’s first deputy. Helen sells her store for $2,000 so she can leave. Will sees Amy in the lobby and goes to Helen’s room. She knows that Frank Miller is out of prison. Amy learns that Helen was friends with Frank and Will.
In the saloon Harvey says he quit. Ben Miller comes in and is popular. A man says that Will will be dead soon after Frank gets off the train; Will hits him. Will asks for deputies, but no one volunteers. Sam Fuller (Harry Morgan) has his wife tell Will he is not home. A drunk asks Will for a gun to help but is put off.
Harvey finds Helen packing, and she rejects him. Will goes to church to ask for help. Mayor Jonas Henderson (Thomas Mitchell) sends the kids out and leads a discussion. People express their views. Jonas asks Will to go to avoid trouble.
Will goes to retired marshal Martin Howe (Lon Chaney Jr.), who declines to go with him. Amy calls on Helen and asks her to let Will go. Helen says that she is leaving too. Amy says her father and brother were killed, and she became a Quaker.
In the stable Harvey asks Will if he is scared. Harvey tells Will to take a horse. They fight, and Will knocks him out. Helen urges Amy to stay with her man. Herb tells Will that he won’t commit suicide with him, and Will sends him home. Will writes his will. At noon the train is heard.
Will sees Amy and Helen driving to the station. Frank Miller (Ian MacDonald) gets off the train and is given his gun. The four men and Will walk in the street. Will hides and calls out. They shoot. The train leaves, and Amy runs to see a man dead. Will climbs up into a hayloft and kills another man. Frank starts a fire. Will frees the horses and rides one that is shot. Amy shoots Pierce in the back, and Frank takes her hostage. Amy struggles free, and Will kills Frank. Will and Amy embrace. Will throws down his badge and drives with Amy out of town.
In the midst of Hollywood blacklisting some interpreted this as an allegory of many people afraid to stand by a person in danger. Yet the “hero” is as violent as the “bad guys,” and even a Quaker is shown killing in this classic western.