Through the death of her father, Caroline McKay comes into ownership of the McKay Stage Line, running between Prescott and Chino, Arizona. She is unaware that her uncle, Charles Lait, who runs the line for her, is secretly plotting with Dude Elliott to force her to sell out at a low figure. Elliott henchman Pete Branagan, while Caroline is a passenger, holds up the stage and attempts to take the mail, but the hold-up is foiled when Dan Clark, a postal inspector on the way to Chino, rides up and drives off the bandit. Caroline offers Dan a job as a driver, not knowing his real job, and he accepts so he can investigate the situation. Dan induces the miners to send their gold to Prescott as mail shipments via the stage. Knowing that a successful robbery will lose the mail contract for the McKay line, Elliott plans to have Lait rob the safe that night.