Agreeable Regency romance--with spiky, country-bred orphan Sydney squaring off against her new guardian: handsome Andrew Innis, Marquess of Lyle (her father's choice). Sydney arrives at Lyle in hoyden, muddy-cloak style--after being kept waiting at the coach station. And Andrew looks at Sydney askance, turning her social tutorship over to good-natured Cedric Maitland--who has quite a job, since Sydney is too intellectual and too prone to hearty country honesty. (""Society,"" confides Cedric, ""is a system of polite deceit."") Finally, then, with French lessons and new couture, Sydney is brought to London by twittering Aunt Prudence, dutifully becoming a mindless toast of the ton. Yet, still yearning for culture, Sydney persuades a tiresome suitor to take her to an art exhibition. . . where she sees beautiful Lord D'Arcy, an esthete of towering ego who persuades Sydney to support him--in disguise, of course--in his reading of The Tempest at a garden fete. And when Sydney outshines D'Arcy, he ragefully reveals her identity--which leads to duels, proposals, and Andrew's inevitable confession of love. Airy and easy, with more frolics and quips than most of the genre.