Poor but ambitious Lizzie Greystock marries the wealthy Sir Florian Eustace and soon becomes a young widow, after which she refuses to surrender a valuable diamond necklace that her husband had allowed her to wear and insists that it was given to her outright. The Eustace family lawyer, Mr Camperdown, regards the necklace as a family heirloom and demands its return, while Lizzie protects herself by inventing an increasingly elaborate story about her ownership of the jewels. Meanwhile her cousin Frank Greystock, who is engaged to the governess Lucy Morris, becomes involved in her affairs, and Lizzie accepts a proposal from the respectable politician Lord Fawn. As Fawn learns more about the disputed diamonds and Lizzie’s character, however, he begins to regret the engagement, and her lies about the necklace start to threaten both her romantic ambitions and her social position.
