 During the gold rush days a wagon train is attacked by a gang of renegades. John Knox (Steve Clark) is killed and one of his young sons,Asa Knox (Rex Lease), is kidnapped by the renegade leader (Blackie Whiteford.) The other son, Clint (Hoot Gibson), and his mother Martha (Nina Guilbert) escape and reach St. Joseph, Missouri.Clint grows up and becomes a crack rider for the Pony Express. The kidnapped brother, now known as Ace Carter, has been raised by the outlaws with a contempt for the law. He is an unsuccessful rival of Clint s for the Pony Express job, which fosters enmity between them. Ace holds up a stagecoach on which Martha Knox and Clint s sweetheart, Mary West (Marion Shilling), are passengers. Clint takes the trail and runs him down. Clint later learns Ace s true identity and saves him from a lynch mob. Because of the circumstances, Ace;s captors relent, and the two brothers and their mother are reunited.