George Mars has had one passion since childhood: customized rifles and hand guns. He lives in the small border town of Pueblo Juárez, where a freighter shot and killed Jorge Español in a gunfight. When Jorge's brother, Hernando, is wounded trying to avenge his death, George Mars decides to customize a Colt revolver in a way that will give Hernando the upper hand next time.
Not long after, the gun is stolen from George's shop. Mars has engraved his name on it but, as the weapon passes from one hand to another, his identity becomes as much a mystery as why possession of it skews the odds in any gun duel.