Synopsis: Riding atop his swift, ebony stallion Black Jack, Federal Marshal Allan "Rocky" Lane attempts to prevent Henry Mason (Roy Barcroft) a crooked railroad agent, from cheating dozens of Cedar Rock ranchers out of their valuable property.
In order to prove that the ruthless swindler is a murderer, the marshal convinces a prison warden to let prisoner Bill Anderson escape from the state penitentiary. The Marshal believes Anderson will lead him to Mason's gang and evidence he needs to lock up the culprits.