In Mexico, expatriate American
pistolero Martin Brady is employed by the Castro brothers, Marcos (
Víctor Manuel Mendoza), a general, and Don Cipriano (
Pedro Armendáriz), the new governor. On a business trip to the United States to arrange the purchase of a wagonload of rifles and ammunition, he is delayed when he breaks his leg in an accident in the Texas border town of Puerto. Treated by Dr Stovall (
Charles McGraw), he stays with German immigrant Ben Sterner (
John Banner), who is the seller of the rifles, and Ben's nephew Ludwig (Chico) (
Max Slaten). Brady's help is sought by the local U.S. Army commander, Major Colton (
Gary Merrill), to persuade Cipriano Castro to cooperate with Colton's
Buffalo Soldiers in an expedition against hostile
Apaches in Mexico. In the meantime the rifles Brady purchased for Castro have been stolen. Captain Rucker of the
Texas Rangers knows Brady fled to Mexico as an adolescent after avenging the murder of his father, not knowing the man he killed was an outlaw. Rucker tries to enlist Brady as a Ranger. Brady is attracted to Colton's unhappy wife Helen (
Julie London). Brady shoots a man named Barton (
Chuck Roberson) who murdered Ludwig and drew on him. He then returns to Mexico to inform Cipriano Castro of the missing rifles. Major Colton and Helen arrive to meet with Cipriano, arranged by Travis Hight (
Jack Oakie), the representative of a railroad threatened by the Apaches. Helen and Brady have a brief affair. Cipriano tells Brady that, by law, he must pay a debt for the rifles and orders him to assassinate his brother Marcos, who seeks to make himself governor. Brady refuses and finds himself an outlaw in Mexico as well. Weeks later on the run, he finds cavalry sergeant Tobe Sutton (
Satchel Paige) and returns with him to Major Colton's camp. Colton has been seriously wounded in a skirmish with the Apaches but is determined to rendezvous with Captain Rucker and General Castro's troops. En route they recover the stolen rifles from a small band of Apaches, but Colton dies. The rifles are returned to General Marcos, who reveals that Cipriano is also dead and he is now governor. Calling Brady an assassin, he demands the Americans surrender him and leave Mexico immediately. Rucker offers to help Brady prove that the shooting in Puerto was a case of self-defense, if he will return to Texas. Brady decides to risk it and heads towards the Rio Grande to be with Helen. Near the river he is ambushed by a gunfighter frequently seen with Marcos. Brady kills him but his
Andalusian stallion, a constant companion throughout the story, is killed. Brady leaves his gun, bullets and sombrero by the horse and walks towards the U.S. ==Cast==