(from: Wilkie Collins: An Illustrated Guide © Andrew Gasson 1998, used with permission)
The 'Overture' is set in the London Foundling Hospital. In 1835 a woman who has left her child there begs to know the new name he has been given, and is told it is Walter Wilding. In 1847 she returns to adopt the boy called Walter Wilding, whom she believes to be her son.
Wilding grows up to be a successful wine merchant and in 1861 takes a new partner, George Vendale. On his first day Vendale visits Jules Obenreizer, the English agent for the firm's Swiss champagne supplier Defresniers. He meets Obenreizer's niece, Marguerite, and they fall in love despite Obenreizer's attempts to prevent their relationship. Wilding, meanwhile, learns from his new housekeeper, once a nurse in the Foundling Hospital, that he is not his supposed mother's son. That boy had been adopted and taken abroad, and a second boy given the same name. He determines to find the rightful owner of his fortune. All his investigations end in 'no thoroughfare' and he dies shortly after.
Vendale now learns that a remittance to Defresniers has been stolen and he must deliver personally a forged receipt so that the criminal's handwriting can be identified. The thief is Obenreizer who volunteers to travel to Switzerland with Vendale, hoping that he can recover the evidence. While they attempt to cross the Simplon Pass in a blizzard, Obenreizer confesses his guilt. He has drugged Vendale and intends to leave him to die on the mountain. Marguerite, however, has followed with Joey Ladle, the head cellar-man, and rescues Vendale from the edge of a precipice. They later confront Obenreizer who maliciously reveals that Vendale is illegitimate. He is, in fact, the true heir to Wilding's fortune. Vendale marries Marguerite and Obenreizer perishes in an avalanche.