My second favorite Heyer, another one I've reread a few times. It's very different in tone and atmosphere, and indeed, plot, from her other books. Prudence and and her brother Robin have spent most of their lives pretending to be other people. They are adventurers, and have participated in many wild schemes dreamed up by their father, the 'Old Gentleman'. Their most recent exploit was participating in the failed attempt to restore King Charles to the throne. In order to escape exposure of Jacobites, Prudence and Robin change not only their identities, but their genders. Prudence becomes Peter and Robin his sister Kate. Peter and Kate become the toast of the town, as they await the arrival of their father... Cross dressing twins, mistaken (and revealed) identities, swindles, intrigue, masked balls...it has everything, including a twist so unexpected that I exclaimed outloud and then spent the entire day explaining it to my family, none of whom really cared. (Also went around saying things like 'Lud!' and prefencing sentences with 'La', and generally talking like it was the 18th century.)Lastly, Robin is my favorite forever.