Autry Braden with his partner Ed Talley aim to make their fortune and join the unscrupulous and murderous George Mason to hunt mustangs in 1804 Spanish Texas across the Sabine from Louisiana Territory. Their mission intersects with Maria Manuel, who is running from the vicious Juan Castenada, captain of the Spanish garrison at Nacogdoches, who has violated Maria and had Mason kill her husband so he could claim her as his wife.
As Maria escapes Castenada's horrors, she takes refuge with the mustanging trio where Braden protects her from the vile Mason as they move west of Nacogdoches into the country of the Wichita and Lipan, who are enemies. The Wichita want to trade for Maria, but Mason realizes her value to Castenada, so he offers them half of their mustang haul when they return, but all of the animals will come out of Braden's and Talley's share. This creates animosity among the three men.
When they reach the village of the Lipan, the chief's son wants Maria instead of trade goods. When her trade is refused, the warrior Galls challenges Braden to a fight for her. Braden wins but creates an enemy in Galls who must destroy Braden to win his honor back.
After leaving the Lipan camp, the party moves into mustang country where they encounter the legendary golden stallion and his brood of 200 mares. They work weeks to acquaint the mustangs with their presence, build a pen to trap them in and trail brake them once they are captured. Braden captures the golden stallion and breaks it for the return to Louisiana Territory.
In the interim, Castenada has decided to pursue the mustangers, take Maria and claim the mustangs for his own. The Spanish locate the mustangers but remain hidden to spring their trap closer to Nacogdoches to make it easier to claim their spoils.
On the return trip toward the Sabine, all the interweaving animosities of the mustangers, the Spanish, the Lipans and the Wichita boil over in a variety of showdowns, some with expected outcomes and others with unforeseen resolutions.
