During the Franco-Mexican War, ex-Confederate soldier Ben Trane (Cooper) travels to Mexico seeking a job as a mercenary. He falls in with Joe Erin (Lancaster), a gunslinger who heads a gang of cutthroats (Ernest Borgnine, Jack Elam, Charles Bronson, Archie Savage, and others). They are recruited by Marquis Henri de Labordere (Cesar Romero) for service with Emperor Maximilian I of Mexico (George Macready) Maximilian offers them $25,000 to escort Countess Duvarre (Denise Darcel) to the city of Veracruz. Trane gets the emperor to double the offer.