Since the loss of her parents, the beautiful young Filipa Seymour runs the family's ancient Manor House alone with very little money and only her beloved dogs and horses and ageing housekeeper, Mrs. Smeaton, for company. So she looks forward with excitement to every visit from her brother, Sir Mark Seymour, except that invariably he is looking for yet another heirloom in the house to sell in order to finance his extravagent Society lifestyle in London. So when Mark suggests a crazy plan for Filipa secretly to take the place of the glamorous 'Pretty Horse-Breaker' with whom he is due to ride at the Marquis of Kilne's prestigious horse race meeting, she reluctantly agrees. Introduced to the Marquis and the other house guests as 'Fifi', Filipa is intimidated yet strangely enthralled by his dismissive attitude. But, even as she realises that she is falling in love with him, the Marquis seems oblivious to her and convinced that she is just another gold digger - until she foils a dastardly plot to poison his beloved stallion, saving its life and probably that of its rider as well and in the process opening the Marquis's eyes to love.