US marshals Ken, Hoot and Bob stop a gang dressed as Indians from robbing the stage. After getting repairs at the relay station, but before they get to town, another trap is set, but they get away. In town, they search the stage and find nothing. But hidden in the axle grease can are diamonds. Polini wants them cut into smaller diamonds so that he can easily dispose of them. Throughout this Western, the courageous trio faces off against cunning opponents, including the gang's merciless leader (Ian Keith) and an unsuspecting banker (Karl Hackett).
as Ken Maynard
as Hoot Gibson
as Bob Steele
as Ruth Hampton
as Polini
as Warren, the Jewel Cutter
as Banker Steve Lynch
as Henchman Duke Rollins
as Engineer Jim Lockwood
as Henchman Ace
as Ted Hodges (as Chas. Murray Jr.)
as Henchman
as Henchman Bates
as Henchman
as Donny Davis
