Watch Pirates of the Prairie for Free: How to Stream the Movie Online at 123Movies. . In one of his better early Westerns, Tim Holt, as Deputy Marshal Larry Durant, is sent to Spencerville where a gang of vigilantes has been terrorizing the citizenry. Going undercover as a gunsmith, Larry quickly learns that the leader of the vigilantes, John Spencer (John Elliott), is an honest man who only seeks to establish law and order. The real brains behind the crimes, meanwhile, are revealed to be Spencer's brother-in-law, Lou Harmon (Roy Barcroft), and his chief henchman, Leighton (Charles King), who speculate in the coming of the railroad by forcing the townspeople to relinquish their land.