Having accepted the sheriff's job in Red City, Lucky Luke arrives to find a town entirely under the control of Pat Poker, a ruthless gambler, cheat and saloon owner, and his henchmen. His horse, clothes and revolver stolen, Luke decides to pass himself off as a harmless, bumbling tenderfoot, all the better to study his opponents and catch them unaware. Still, Pat won't give up easily, and keeping him behind bars might require some additional work...