Trouble brews when Bronco is leading a wagon train through the wilderness. It seems that an old army buddy of his is on the train, and he's brought along the runaway daughter of a powerful cattle rancher, who doesn't like it one bit.
Bronco arrives in a small town right after a stagecoach robbery in which a man has been killed. Suspicion immediately falls upon him, and what he doesn't know is that the robbery was actually committed by an old friend of his.
The outlaw Traxel brothers and gang leader Willis Turner murder Bronco's best friend and then frame him for the crime. He is sentenced to hang, and the only thing that can save him is the testimony of a young girl who knows that Bronco didn't do it--but she's a mute.
Outraged at becoming unwittingly involved in a payroll robbery and murder, Bronco sets out to find the killers and bring back the money. He doesn't have a whole lot of time, however. A posse is forming and they're going after who they believe to be the real killer--him.
Bronco is hired to deliver a riverboat to his friend Martha Chandler. He hasn't counted, though, on a ruthless businessman who doesn't want the ship to complete the trip, and a beautiful blonde passenger who has her own agenda.
Cattlemen and sheepmen are in dispute over grazing rights on the range. Bronco doesn't want to get involved but has to step in before a range war breaks out, mainly because the sheepmen are Quakers who refuse to carry guns and the cattlemen have no such qualms.
Pursued by Marshall Gaffney for a robbery he did not commit, Bronco rides to the town of "Last Resort" -- a hideout for outlaws on the Mexican border run by Three Fingers Jack. There Bronco hopes to clear his name by finding the real robber -- a charming but treacherous man named Billy Styles.
Bronco hires a mother and son who are refugees from the fallen empire of Emperior Maximilian of Mexico, but he soon discovers that bandits who believe the two know where $5 million in gold is buried are after them.