The first edition of Charles Dickens's novel Our Mutual Friend (1864–1865) included a slip of paper at the beginning of the volume, advising that the astute reader would understand the meaning of the title when they reached Chapter Nine. This 'detective' fiction, promising a game of plot mysteries, continues in the book itself: the story of London 'millionaire dustman' Harmon, who made his fortune through municipal contracts; his heir, John, declared dead; and the capricious beauty Bella Wilfer, a girl from a poor family dreaming of a profitable marriage; it is built on identity substitutions, disguises, and sudden revelations, and contains episodes of blackmail, attempted murder, and other hallmarks of a crime novel. Dickens's last completed novel, Our Mutual Friend, develops the themes of human duality, the search for one's true self, and freedom of choice in life, which would become central to the writer's final masterpiece, the intriguingly unfinished detective novel The Mystery of Edwin Drood.