Unemployed reporter Chick Williams wins a racehorse, Special Delivery, in a dice game. His girlfriend, Anne O'Malley, runs the hamburger stand at the racetrack, and having grown up with horses, is an experienced trainer. Chick and Anne discover that Special Delivery is a born champion, and have him poised to race in the high stakes "King's Plate." Their horse is a shoe-in to win and the broke sweethearts are counting on the prize money so that they can marry. But the night before the big event, gangsters blackmail Chick into believing he MUST throw the race that he's sacrificed everything to win!

Movie sex siren Toby Wing was as well known for her high-profile romances with Jackie Coogan, Maurice Chevalier and Franklin D. Roosevelt, Jr., as she was for her acting. Thoroughbred affords her a rare starring role and she makes the most of it. Character actor Kenneth Duncan is best remembered for his roles in Ed Wood's Night Of The Ghouls (1959) and The Sinister Urge (1960) as well as The Astounding She-Monster (1957).