 On their way to Sonora Mary Burton(Shirley Palmer) and Patsy Ellis(Ann Fay)are motoring through Arizona and stop in Twin Forks, and meet cowhand John Bishop(John Wayne)and his horse Duke(Duke the Miracle Horse.)John, preparing to drive a coach in the big stagecoach race,innocently says that with Mary pulling for him, the other coach will probably fall to pieces before it gets around the first curve.Unkinown to John, townsman with heavy bets on John s coach have tampered with the other coach which piles up in a horrible wreck.Circumstantial evidence and his own words points to John and he is jailed as the injured driver is carried off.Assuming his guilt Mary and Patsy motor on to meet up with Mary s father(Ralph Lewis)at his silver mine across the border in Mexico.Knowing he is innocent,John s employer Bob Leadly(Henry B. Wathall) and ranch hands Shorty(Bill Franey) and Riley(Frank Rice)spring John from jail and urge him to ride for somewhere in Sonora.John aks Leadly why he took such a chance on him and Leadly tells him of his own son,Bart(Paul Fix), who fell in with the wrong crowd and was falsely accused of murder.Bart is now across the border riding with the notorious outlaw Monte Black(J.P. McGowan)in the Brotherhood of Death, so named because anyone who tries to leave the gang is killed. John vows to bring Bart back to Arizona where he has been cleared of the crime, and is joined by Shorty and Riley, who tell him he has also been cleared by the recovery of the stage driver.In a Mexican cantina, the trio meets up again with Mary and Patsy, who have traded their car for a buckboard and the girl s still distrust him until he saves them when their wagon runs out of control, and Shorty and Riley set the record straight on John.John is told by Mary s father that the Mexican Rurales under Captain Ramirez(Joe Dominguez)have been pursuing Black s gang and, when one of Black s men is captured,learn the location of the gang s hideout.John rides out alone hoping to rescue Bart before the Rurales attack and Black, who was impressed at how John handled a saloon-full of Black s henchmen, takes him on as another gun.The gang rides out to raid the mine office at Paloma but John sends "Duke" ahead and the wonder horse, courtesy of stock footage of "Tarzan" from Ken Maynard s earlier "Somewhere in Sonora",beats the raiders to Paloma and pulls the warning-bells rope.The gang members that escape capture John and Bart but Duke(and Tarzan) again saves the day by leading the Rurales to the spot.Just curious, but who decided that a cast listing that didn t include the credited Duke the Miracle Horse could be "verified" as complete?