Lord Rule was to marry Elizabeth, but she was in love with an Army Lieutenant.  Elizabeth's youngest sister, Horatia, goes to Lord Rule and offers herself as a substitute bride.  Lord Rule instantly likes Horatia and agrees to marry her, since he was only getting married to produce an Heir.  This is a sweet love story. It kept my attention and has many twists and turns.  I am particularly fond of Lord Rule for his correct and humorous speech throughout the story.  I highly recommend this book.  It is one of my favorite novels by Georgette Heyer so far.