Lucky Gagin (Robert Montgomery) arrives on a bus in San Pablo, a small rural town in New Mexico, during its annual fiesta. He plans to confront and blackmail a mobster named Frank Hugo (Fred Clark) as retribution for the death of his best friend Shorty. He unpacks a Colt .45 pistol from his luggage, sticks it in his waistband, places a check which incriminates Hugo in locker 250, and hides the locker key behind a framed map in the bus depot waiting room using a piece of chewing gum.