The Eustace Diamonds

Warning: wikipedia contains spoilers

In this novel, the characters of Plantagenet Palliser and his wife, Lady Glencora, are in the background. The central plot concerns Lizzie Greystock, a fortune-hunter who marries Sir Florian Eustace and is soon left a wealthy widow. The diamonds of the book's title are a necklace, a Eustace family heirloom. Lizzie attempts to hold on to them, while searching for another suitable husband. After falling out with a potential suitor, Lord Fawn, over the diamonds, she marries the disreputable Mr Emilius, a foreign clergyman who is already married. Her hopes of retaining the Eustace diamonds are eventually dashed.