Republic, in pre-production trade announcements, had John Wayne slated as the star of this film but cooler heads, once the script was read, realized that Wayne wasn't exactly the dual-role, twin brothers type. The film opens by establishing that, as young boys, David Cook and twin brother Tom are poles apart in disposition and traits. When their father dies, Tom goes to New Mexico to live with his Uncle Hardtack while David remains behind to care for their mother. The grown Tom becomes an outlaw while brother David becomes a government lawman. David is charged with apprehending Tom and also two other renegades, Hardman and Marsden, both bitter enemies of Tom. Unable to arrest Tom in his home territory because he is in league with crooked sheriff McDaniels. Tom is lured home by a fake telegram telling him his mother is dying and put in jail. David, posing as Tom, goes to Mesa City, New Mexico and undertakes a campaign to obtain evidence to convict Hardman and Marsden. He persuades the latter to pool their interests in one gang, under his leadership. Tom had been romancing Phyllis O'Conover, an entertainer at the Bonanza Cafe, and Phyllis' older sister, Julie, has been working hard to break up the romance. David, posing as Tom, has to continue the pursuit of Phyllis, but finds himself falling in love with Julie. Julie learns Tom's real identity and agrees to marry him but Phyllis, thinking her sister is taking from her the man she believes to be Tom Cook, threatens suicide. The broken-hearted Julie urges David to marry Phyllis and David, much against his own desires, carries out Julie's wishes. Meanwhile, Hardman, Marsden and McDaniel have discovered David's real identity and plot to get rid of him. And in another meanwhile, Tom escapes, returns to town and, finding that Phyllis has married David, kills her for what seems to him to be her unfaithfulness, never mind that she thought David was Tom. Some days, a good girl just can't get a break. Tom and the other outlaws are lined up against David in a gun battle when Pima, Tom's Indian servant, who has long hated him for his cruelties, brings a large force of Indians to David's aid. Tom attempts to kill David, but Uncle Hardtack shoots him first. Some days, a bad guy just can't get a break either.