Outlaw Duke Santee stumbles across the opportunity of a lifetime when he meets a sacked railroad employee who wants to get even with the Company. Never one to pass up a golden opportunity, the gang boss offers to help him rob the Flagstaff Flyer. Unfortunately, the plan backfires as Santee has little experience of using the high explosives which destroy the train's express car as well as its payroll shipment. However, all is not lost, for a newspaper reveals that a dynamite man called Lee Jago is being transferred to Yuma prison by wagon. Santee wastes no time in organising a rescue mission, but that is only the beginning of the troubles that will ultimately bring Santee to justice.