Wandering horse trader Roy Rogers approaches palomino breeder Gabby Kendrick at his Golden Horse Ranch about the possibility of mating his horse Lady with Gabby's champion Golden Sovereign, but Gabby coldly refuses. That night during dinner at host Brett Scoville's El Dorado club, Roy makes another attempt to interest Gabby in Lady, but is thrown out of the club. Scoville arranges to let Gabby win at gambling, then sends two of his henchmen to steal Sovereign, whom he wants on his own ranch to breed champion horses. The men steal Sovereign, but the horse proves too powerful for them and runs off to be with Roy's mare. When Sovereign's disappearance is discovered, Gabby and his hands call on Scoville to help search for the horse. The next morning as Roy leaves the area, Scoville and his men come across Sovereign in a small corral fighting a wild black stallion. Scoville attempts to shoot the black stallion and instead kills Sovereign. Roy, hearing the shots, goes to Sovereign's aid, and is discovered by Gabby and his daughter Susan, who accuse him of killing their prize horse. Roy is arrested and when a bondsman, Wallace, offers Roy bail in exchange for Lady as collateral, Roy refuses and takes his horse, becoming a fugitive. Many months later, Lady gives birth to Sovereign's heir, whom Roy names Trigger. Later when young Trigger is attacked by a mountain lion, Lady comes to his aid, but is fatally injured. Roy raises Trigger and after a year returns to the Golden Horse Ranch to offer Gabby Sovereign's son, but the old man stubbornly declines. In Roy's absence, Gabby has gambled recklessly at the El Dorado and Scoville holds a high number of his IOUs. Scoville tries to goad Gabby into selling the ranch, and even though Gabby turns him down, he remains concerned about how to repay Scoville. Roy turns himself in to the sheriff, but as he only has part of the money to repay the bondsman, Trigger is put up for auction and purchased through a third party by Scoville, who hopes to use him against Gabby. Unknown to all, Susan has the charges against Roy dropped and he is released from jail. Meanwhile, Scoville succeeds in tempting Gabby into betting the entire ranch on a horse race, without telling him he owns Trigger. Scoville then offers Roy the opportunity to race Trigger against Gabby's Golden Empress and he agrees. On the day of the race, Roy finds out both that Susan was responsible for freeing him from jail and that Gabby has wagered the ranch on the race results. Roy tries to pull out of the race but Scoville convinces him to stay on by offering him Trigger if he wins. During the race Susan, riding Golden Empress, is boxed in by Scoville's other riders. When Roy notices, he intervenes, letting Susan win the race. Meanwhile, Roy's friend Bob has taken Scoville's henchmen to the sheriff to implicate Scoville in Sovereign's death. Trigger is returned to Roy and mated with Golden Empress, who later gives birth to twin colts.