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).