A body pulled from the Thames is identified as young John Harmon, heir to a fortune made in dust-contracting (a lucrative 19th century recycling business). Bella Wilfer, his wife-to-be by terms of old Harmon's will, goes into mourning though she has never met her fiancé. Bella is adopted by Mr. and Mrs. Boffin, inheritors of the dust business in default of young Harmon. The Boffins also hire a very capable but mysterious young man as secretary, John Rokesmith, whose keen interest in Bella holds the secret to his true identity.