 The film begins at Royal Ascot where we quickly learn that Col Keene (Wilfrid Hyde-White) is a keen aristocratic gambler.He is a dissolute Irish baronet who gambles away his ancestral home and its racing stables to Sir Charles Hare (Terence Morgan), who decides to stay on when the new American owner's attractive daughter Pat (Peggy Cummins) mistakes him for a groom.Playing along with her mistake, romance develops between the two, as Hare helps Pat rear a colt to enter into the Derby Day competition.