 Wealthy sportsman Colonel Ross asks Holmes to investigate the disappearance of his prize thoroughbred Silver Blaze, whom he wants to enter in the Wessex Cup Race. On the night in question the stable is visited by a gambler hoping to get some inside information on the race but is turned away by a loyal stable boy. After the boy is drugged by opium, the horse disappears, and the trainer is found bludgeoned on a lonely moor, suspicion falls on the gambler, but if he is guilty, where is Silver Blaze?