Captain Terrance Connaughton loses his stable of horses in a card game with Algernon Cravens. The next day he is wounded and taken to a military hospital where he meets and falls in love with Lady Gwendolyn. An attack on the hospital separates them and, at the end of the war, Terrance returns home penniless. Cravens, the cad, has made Lady Gwen promise to marry him and has entered the horses he won from Terrance in the National Derby. Terrance goes to London to attend the Derby and sees Lady Gwen again. She is less than thrilled with the prospect of marrying Cravens and makes him a sporting proposition; if "Bad Luck" wins the race she will marry him immediately but if "Good Luck" wins, their marriage will never take place, and she and Terrance will be free to resume their romance. "Bad Luck" wins and Cravens comes to claim his bride, but two of the stable-boys discover that Cravens had the distinguishing marks on "Good Luck" painted over, and it was really "Good Luck", of the two nearly-identical horses, that won the race. The jig is up for Cravens.