Macreedy is looking for a man named Komoko but the residents are inexplicably hostile. At the hotel, the young desk clerk, Pete Wirth (John Ericson), says all the rooms are full. The newcomer is none-too-subtly threatened by local tough Hector David (Lee Marvin). Reno Smith (Robert Ryan), the town's leading citizen, tells Pete to give Macreedy a room. Smith informs Macreedy that Komoko no longer lives in Black Rock; as a Japanese-American he was interned for World War II.
Certain something is wrong, Macreedy sees the town sheriff, Tim Horn (Dean Jagger), but the lawman is an alcoholic and clearly afraid of Smith. The town physician and undertaker, Doc Velie (Walter Brennan), advises Macreedy to leave town immediately. Smith lets slip that Komoko is dead. Liz Wirth (Anne Francis), Pete's sister, rents Macreedy a Jeep. Macreedy finds Liz to be the only civil person in town.
Macreedy drives to nearby Adobe Flats where Komoko lived. He finds the homestead burned to the ground. He finds plenty of water in the well and a patch of wildflowers growing in the dust. On the way back Coley Trimble (Ernest Borgnine) tries unsuccessfully to run him off the road.
When Macreedy returns, Smith learns that Macreedy lost the use of his arm fighting in Italy. Macreedy tells him he found a grave at the Komoko place at the only spot where wildflowers are growing. He suspects that Komoko's body is in it. The guess scares Smith. Macreedy discovers that Smith is a virulently anti-Japanese racist.
Macreedy tries to telephone the state police but Pete refuses to put the call through. Doc Velie admits that something terrible happened four years ago and Smith has everyone too terrified to speak up. Velie offers to drive Macreedy out of town in his hearse but Hector walks up and rips the distributor cap and spark plug wires out of the engine.
Macreedy then dictates a telegram to Hastings (Russell Collins), addressed to the police. While Macreedy is having lunch Trimble picks a fight with him but Macreedy uses karate to knock him out. Macreedy tells Smith that he knows Smith killed Komoko and was too cowardly to do it alone, so he had to involve Hector, Pete, and Coley.
Macreedy spends the night sitting in the hotel lobby, hoping that Smith and his men won't dare attack him in such a public place. Smith and his henchmen are already there. Hastings tries to give Smith a telegram but Macreedy snatches it away. It is his own unsent message. Doc Velie accuses Hastings of committing a federal crime and demands that Sheriff Horn do something. Horn tries to confront Smith, but Smith just takes his badge and gives it to Hector. Hector tears up the telegram.
After Smith and Hector leave, Macreedy and Velie attempt to get Horn to enforce the law. He refuses to become involved. Macreedy works on Pete who finally tells him what happened in 1941. Komoko leased some farmland from Smith, who knew that there was no water there. However, Komoko dug a well and found some, making the land valuable. Smith was unable to break the lease. After the attack on Pearl Harbor, Smith was turned down for enlistment. He and the other men spent the day drinking, then decided to scare Komoko. The old man barricaded himself inside his home, but the men set the place on fire. When Komoko emerged with his clothes on fire, Smith shot him, much to Pete's surprise.
Macreedy finally reveals his motivation. Komoko's son died trying to save Macreedy's life in combat and he was bringing the son's medal to his father. The loss of his arm had left Macreedy wallowing in self-pity and despair, but Komoko's murder gave him a purpose again.
Pete gets his sister to bring the Jeep. Pete then lures the watching Hector into the hotel office where Doc Velie knocks him out with the metal nozzle of a fire hose. Liz drives Macreedy out of town.
When Liz stops the Jeep in a canyon Macreedy realizes he has been betrayed. Smith begins firing at Macreedy who shelters behind the Jeep. Liz rushes to Smith despite Macreedy's warning. Smith tells her she has to die along with the rest of his accomplices. He shoots her in the back when she runs. Macreedy finds a discarded bottle and fills it with gasoline, creating a Molotov cocktail. When Smith climbs down to get a better shot Macreedy throws it; Smith is splashed with burning fuel.
As dawn breaks, Macreedy drives up to the town jail with the injured Smith and Liz's body. Velie and Horn rush out. They had mustered up enough courage to jail Hector David and Coley Trimble. The state police are called in to take the murderers away. As Macreedy gets ready to leave, Doc Velie asks him for Komoko's medal to help Black Rock heal. Macreedy gives it to him and boards the train.
The film's producer, Dore Schary, wanted Spencer Tracy as Macreedy. Concerned that Tracy might not agree, Schary ordered the script changed so that Macreedy was a one-armed man. He rightly concluded that no actor would turn down the chance to play a character with a handicap.
This was Spencer Tracy's last film for MGM. This was MGM's first motion picture to be filmed in Cinemascope.
Preview audiences reacted negatively to the film's original opening sequence. A new shot showing the speeding train rushing at the camera was created instead. The shot was taken from a helicopter as it flew away from the moving train. The film was run in reverse to create the opening shot.
The "town" of Black Rock, Arizona was built for the film. Today nothing remains of the set() . It was one mile north of the Lone Pine railroad station, a stop on the Southern Pacific Railroad's Jawbone Branch which served the northern Mojave Desert and Owens Valley.
Bosley Crowther, film critic for The New York Times, liked John Sturges' direction and the ensemble acting, writing, "Slowly, through a process of guarded discourse, which Director John Sturges has built up by patient, methodical pacing of his almost completely male cast, an eerie light begins to glimmer... Quite as interesting as the drama, which smacks of being contrived, are the types of masculine creatures paraded in this film. Mr. Tracy is sturdy and laconic as a war veteran with a lame arm (which does not hamper him, however, in fighting judo style). Mr. Ryan is angular and vicious as the uneasy king-pin of the town, and Walter Brennan is cryptic and caustic as the local mortician with a streak of spunk. Ernest Borgnine as a potbellied bully (he was Fatso in From Here to Eternity), Dean Jagger as a rum-guzzling sheriff, Lee Marvin as a dimwitted tough, John Ericson as a nervous hotel clerk and Russell Collins as a station-master are all good, too.