During the Mexican Revolution, a group of bandits led by General El Chucho keeps raiding trains to support their cause. One day, they encounter an American named Bill Tate, who claims to be a sympathizer of the revolution. He quickly proves his value by aiding them in hijacking a government ammunition train. El Chucho, intrigued by Bill's cunning and combat skills, allows him to join their small army. As they undertake various missions to destabilize the oppressive regime, the newcomer brings a combination of ambition and ruthlessness that both aids and unsettles the group.

El Chucho's brother, El Santo, a fervent revolutionary with deep-rooted beliefs, becomes wary of Bill's true intentions. The moral and ideological chasm between the characters begins to widen as they get deeper into conflict. Their alliances are tested further when Bill's true role in the revolution and his enigmatic past start to unfold, leaving El Chucho facing critical decisions that could affect their future and the revolution's cause itself.