Horse breeder Ma Dawson is undergoing hard times. Her adopted daughter, Joan, a Canadian by birth, decides to act on her belief that a horse's bloodline is the most important factor in determining a champion and buys an unwanted thoroughbred. The emaciated colt, named Stormalong, is brought back to health and trained under the watchful eyes of Joan and Ma Dawson's son, Tommy. They eventually enter Stormalong in race after race, and he dutifully wins them all, thereby attracting the attention of an international gambling syndicate. Unable to convince the Dawsons to throw races for them, the syndicate tries first to have the horse doped and then killed in a stable fire. Unsuccessful in these attempts, they eventually shoot Stormalong by sniper fire as it races towards victory in the Melbourne Cup. The horse manages, however, to stay on its feet long enough to cross the line first, before collapsing and eventually dying. Meanwhile, Tommy, who has been kidnapped by the gang, manages to escape and capture those responsible. The story ends with him and Joan deciding to marry.
The story, written by emerging Hollywood writer Edmond Seward, is elaborated with numerous sub-plots, with comic relief introduced by the stable hands and through (satirical) discussions between Joan and the Dawsons' aristocratic neighbour, Bill Peel, regarding thoroughbred people and thoroughbred horses.
