Silent screen Western star Tom Mix portrays a detective investigating a series of train robberies in this fast-paced, stunt-driven oater filmed on locations at Colorado's Royal Gorge. Mix poses as a masked outlaw in order to infiltrate the outlaw gang behind the robberies, only to discover that their leader is the secretary (Carl Miller) to the railroad president (William Walling). Along the way, the hero falls in love with the president's daughter (Dorothy Dwan). Considered one of Mix's very best efforts, this well-staged and photographed Western also benefitted from good performances by the smooth Carl Miller and comedy sidekick Harry Grippe. According to the star himself, John Wayne worked as a prop boy on this film.