When Arabella Grant's wicked aunt dies suddenly, both Arabella and her cousin Lady Isabelle cannot help but feel relieved. She'd made their lives miserable, and now Lady Issie is free to read to her heart's content, and Bella is free from taunts about her ignoble birth.

Their newfound freedom is threatened, however, when Issie's great-aunt commands her to travel to London for a come-out Issie has never wanted. Issie, who is in poor health, is convinced she'll drop dead like her mother did if she drops into a curtsy before the queen. So when her great-aunt turns out to be nearsighted and can't tell the noble Lady Isabelle from her commoner cousin Arabella, Issie convinces Bella to take her place. Bella can attend all the exclusive entertainments that her lower birth would typically exclude her from, and Issie can stay in bed, her nose in a book.

Bella agrees to the scheme for her cousin's sake, but matters turn complicated when she meets the irresistible Lord Brooke. He begins courting her while under the impression she's the rich and aristocratic Lady Isabelle, who, unlike Bella, is a suitable bride for an eligible young earl. And Bella, who is convinced that she has met "Lord Right," worries what will happen when she reveals that he's actually fallen for...the wrong lady.