In a small town in New Mexico known as Hadleyville, Marshall Will Kane who is newly wedded to Amy Fowler is getting ready to retire. The joyous couple are making plans to leave to start a new life, starting a family and operating a store in different town. However, they get word that a radical criminal who Kane had sent to jail, had been set free and would be arriving on the noon train. Miller’s gang which is comprised of Ben, his younger brother, Jim Pierce and Jack Colby, wait for him to arrive at the train station and it becomes apparent that they are seeking revenge.
Amy, who is a Quaker and a pacifist, believes that the solution is simple; leave town before Miller arrives. However, Kane has a strong sense of duty and honor, he refuses to allow them to make him run because he has not run from any criminal before, all through his entire career. He also believes that if he doesn’t face them now, they will eventually hunt him down and kill him. Amy goes on to give train an option to come with her on the noon train or she would leave him behind.
As Amy waits at the hotel for the train to arrive, she meets Helen Ramirez who used to be Miller’s lover, then Kane’s, and discovers that she is leaving too. Amy also knows the reason Helen is fleeing. Helen goes on to tell Amy that if she were still Kane’s lover, she would not leave him during trying times such as these.
Kane tries to gather a posse at the tavern and the church, but a lot of the men are too afraid to help. Some of the town’s people tell Kane to avoid the gunfight entirely as they believe it would damage the reputation of the town. The rest of them who happen to be Miller’s friends are still upset that Kane made the town crime-free.
Meanwhile, Kane’s young deputy Harvey Pell is also upset that Kane did not recommend him as successor and tells Kane that he would only stand with him if Kane goes to the City Fathers and put in a good word for him. Kane turns down Pell’s offer and Pell resigns and his deputy. Kane later heads off to visit old friends. Marshal Howe, his predecessor, is old and arthritic, Judge Percy Mettrick who sentenced Kane to jail runs away on the back of a horse and advises Kane to flee too.
Herb Baker, a townsman, agrees to become Kane’s new deputy but pulls out after he realizes he is the only volunteer. Sam Fuller hides in his home and tells his wife to keep telling Kane that he is not home. Kane goes on to write his will as the click in his office gradually heads towards high noon. At the stables, Pell saddles a horse and tries to convince Kane to leave on it. Their discussion aggravates into an argument and Kane beats up Pell and then heads back into the street to confront Miller and his gang all by himself.
The criminals head towards Kane and then a gunfight ensues. Kane is able to gun down Ben Miller and Colby but gets wounded in the process. As the train gets ready to leave town, Amy hears the gunfire and jumps off, running back into town. Amy decides to place her husband above her religious beliefs and picks up Ben Miller’s gun and shoots Pierce in the back.
With Frank Miller being the only one left alive, he grabs Amy and uses her as a shield to force Kane out of hiding. Amy claws at Miller’s face, causing him to push her to the ground, and this give Kane a clear line of fire, and he immediately shoots Miller dead. Kane goes on to help his wife to her feet and they hug as the townspeople emerge and surround them. Kane goes on to gaze at them with bitter contempt, and without a word, he tosses his marshal star to the ground, and leaves town with Amy on their wagon.