Cassy"" is Lucasta Loring, eldest of three well-bred but penniless orphan sisters in 1813 Leicestershire--but when that arrogant, rich rakehell the Marquis of Allingham (whom she's barely met) offers marriage, Cassy proudly refuses. Instead she decides to save her family from penury (nice maiden aunt Letty too) by secretly going on the stage; thanks to an introduction from Sarah Siddons--an old family friend--she gets an audition at Drury Lane, sings and dances prettily enough to please Lord Byron (on the management committee), and is soon leading a bewigged double life as demure Lucasta back home and luscious Cassandra in London. But guess who starts taking a fancy to rising star Cassandra? The Marquis of A., of course--who has taken many of his mistresses from among the ""doxies"" who trod the boards. And though ""Cassandra"" makes her virtuous nature absolutely clear, the Marquis keeps popping up, slowly but surely winning her heart: he rescues Cassy when she's abducted by the evil ex-actor who's been sending her blackmail notes; he rescues her from the embrace of the Prince Regent (""a vast cream satin bulk"") in Brighton; he helps her in a scheme to break up her cousin's announced wedding to a bona-fide doxy; he even invites her, as Cassandra, to his mother's house and defends her when her honor is questioned. Scandal-conscious Cassy, however, feels that marriage with the Marquis is now impossible, so she almost weds a nice widower-actor and then flees to Paris and Vienna (where that evil nemesis must again be dealt with). So it's only after the Marquis--who seems to suffer from severe myopia--finally realizes that Cassandra is Lucasta that a happy ending can ensue. . . . First-novelist Lyle provides none of the snappy humor one looks for in top-flight Regency romance; and the see-through plot (likewise a subplot about Aunt Letty's returned old flame) is stretched out a tad tediously. But the backstage textures are sturdy, the prose is a bit more literate than the norm, and overall this will not disappoint fans who prefer a bit more gracious heft than usual in their Regency powder-puffs.