South of the Mexican border, Davey, a Chinese boy, is orphaned when his father, whom he only recently met, is killed by thieving white men. The boy is befriended by an Indian named Charley Eagle, whose father was also killed by white men. Charley enters his thoroughbred mare, Black Hope, in a race south of the border and is tricked by Dan Toland, a crooked American, into selling Black Hope to him after she wins the race. Charley returns Toland's money in the night, retrieves Black Hope and returns to his humble ranch in Oklahoma with Davey. Charley's wife Sarah, who is well-educated, insists that Davey attend school, but when the schoolboys tease him because of his yellow skin, Davey refuses to go. Finally, Sarah decides to adopt Davey, and he agrees to begin school. After an oilman gives the Eagles an advance for allowing him to drill on their land, Charley pays for a thoroughbred stud owned by Colonel Caldwell to impregnate Black Hope. The mare is unable to walk following the birth of her male colt, however, and Charley must shoot her. Within months, the Eagles strike oil, and Charley names the colt Black Gold. After the now-rich Charley is hit by a beam at the oil rig, he is forced to walk with a cane. Charley is nonetheless determined to win the Kentucky Derby and arranges for his old friend Buckey to train Black Gold, with Davey as his jockey. One day while training, Buckey's pet goat, Beautiful, crosses Black Gold's path on the racetrack, causing Davey to fall. He is not hurt, but Charley has a heart attack. Charley has often left Sarah unannounced when he has had a yen for the great outdoors, but now he leaves her for good to die alone. She, Davey and Black Gold visit Charley as he camps and hear his last words, "She won." At the Kentucky Derby, Black Gold competes with Toland's favored horse, Corsair, and wins. As Sarah accepts the gold cup from Colonel Caldwell on behalf of all Indians, she repeats her husband's dying words, "She won."