Katie O'Doone is left a worthless, run-down estate and a thoroughbred race horse. She mortgages the property in order to get the money needed to enter her horse in the Derby. Dennis Reilly, a wealthy sportsman, also has a horse in the race and his jockey accidentally runs Reilly's horse into Kate's horse, causing her horse to lose. She swears vengeance on O'Reilly. She is forced to go to work for a crooked bookie, Jake Trumbull, and a crooked competitor of Reilly's,Tod Cuyler, who plan on switching a dead-ringer horse for Reilly's favored-to-win horse, and clean up betting against Reilly's horse.