When her sister takes the proffered chance of a London season under the aegis of their aunt, Clarissa fears her only chance of marriage may come with the stolid and worthy local clergyman. Then, when her impetuous twin suddenly disappears, she steps into the breach and impersonates her in an attempt to placate society and discover her sister's whereabouts.

Clarissa is thrown in at the deep end, surrounded by the modish friends who have known her sister for several months and expect her to be up to date on all the latest gossip and fashions. Not only is her personal maid and confidante already suspicious, but to cap it all, her sister's fiance unexpectedly arrives on the scene. Doggedly, she continues her attempts to find her sister, despite the difficulties inherent in asking questions about the very person she's impersonating, while in the meantime she wards off the advances of her sister's fiance, the devilishly handsome Lord Leighton.

What with his skilful love-making and constant companionship, Clarissa's own heart is soon in danger. They are falling in love, but how can she cheat her own sister of Leighton's attention?