Lord Waincliffe breaks his horse’s bridle while riding one day and calls at the nearest house for help so he can ride home safely. It belongs to Terence Stourton, a professor of literature. He meets the professor’s daughter, Rosetta, who repairs the bridle for him Not only does he think Rosetta is the most beautiful girl he has ever seen, but feels there is something unusual about her. Only when he returns home does he realise that she bears an extraordinary resemblance to his sister, Dolina. Lord Waincliffe and his brother, Henry, are finding it very difficult to afford their house and estate. They have the idea that their wealthy neighbour, the Marquis of Millbrook, could help them build a racecourse on both their estates that would solve all their financial woes. They invite the marquis, who is known for his love of beautiful women, and they expect their lovely sister to help persuade him, but Dolina insists on going to London for a ball instead. They enlist Rosetta to impersonate Dolina for the evening and the marquis is so deeply impressed by her that he agrees to fund the racecourse.