Pulled to a desert island by a wild black stallion he has freed during a shipwreck at sea, then rescued by a southbound freighter, a seventeen-year-old boy befriends the horse, trains him by night, and rides him to victory in a match race.
A boy is entrusted to attend the birth, train, and drive a blood bay colt that is the great hope of an aging reinsman who refuses to be reconciled to the fact that sulky-racing has moved from the county fair to the big night time, moneymaking raceways.
When his wild black stallion revolts against the routine and schedule of stable life, becoming a killer and a threat, a plane crash thwarts Alec's plans to give the Black a free run in the desert and brings danger to both boy and horse.
When the Black is returned to Alec Ramsey, the whole racing world, including Alec himself, wonders which horse is faster: the great stallion or his son, Satan.