(from: Wilkie Collins: An Illustrated Guide © Andrew Gasson 1998, used with permission)
Amelius Goldenheart is in exile from his Utopian community because of an unsanctioned relationship with an older English woman who has suffered some mysterious tragedy in her earlier life--she is the first of the 'fallen leaves'. He comes to London with a letter of introduction to the villainous John Farnaby, and is captivated by Farnaby's niece Regina to whom, after some complications, he becomes engaged. Mrs Farnaby, a woman who 'lives in some secret hell of her own making, and longs for the release of death' enlists his help to look for the illegitimate daughter she lost sixteen years earlier. Farnaby had seduced his employer's daughter in order to force her into marriage and further his own career, but when the baby was born he kidnapped it and gave it to a baby-farmer.
On the streets of London, Amelius is accosted by a 16-year-old prostitute, Simple Sally, and takes her home with him to save her from a life on the streets. They live together as brother and sister, but when Regina discovers her presence she rejects Amelius, breaking off their engagement. Sally turns out to be Mrs Farnaby's long-lost child and they are reunited at Mrs Farnaby's death-bed. Amelius and Sally then marry. The 'Second Series' was intended to follow the course and breakdown of their marriage.