The third and least political novel of the Palliser series, The Eustace Diamonds concerns the beautiful pathological liar Lizzie Greystock. Determined to marry into wealth, Lizzie snares the ailing Sir Florian Eustace and quickly becomes a widow. Despite the brevity of their marriage, Lizzie still inherits according to the generous terms of Sir Florian's will, which include the Eustace diamonds. When the Eustace family solicitor, Mr. Camperdown, begins to question her legal claim to the family heirloom, Lizzie begins to weave a tangled web of deception and crime to gain possession of the diamonds.

Enlisting the aid of her cousin Frank Greystock, much to the dismay of his fiancée, Lucy Morris, Lizzie seeks to both avoid legal prosecution and have a true love affair, first with Frank, and later with Lord George de Bruce Carruthers. Considered a satire of the acceptance of the corrupting influence of money and greed in Victorian society, Trollope's novel blends elements of mystery, politics, and romance in a memorable and thought-provoking work.