At the start of the novel (George Eliot)

Godfrey Cass, Dunsey's elder brother, harbours a secret past. He is married to, but estranged from, Molly Farren, an opium-addicted working-class woman living in another town. This secret prevents Godfrey from marrying Nancy Lammeter, a young middle-class woman. On a winter's night, Molly tries to make her way to Squire Cass's New Year's Eve party with her two-year-old girl to announce that she is Godfrey's wife. On the way, she collapses in the snow and loses consciousness. The child wanders away and into Silas' house. Silas follows the child's tracks in the snow and discovers the woman dead. When he goes to the party for help, Godfrey heads outdoors to the scene of the accident, but resolves to tell no one that Molly was his wife. Molly's death, conveniently for Godfrey and Nancy, puts an end to the marriage.

Silas keeps the child and names her Eppie, after his deceased mother and sister, both named Hephzibah. Eppie changes Silas' life completely. Silas has been robbed of his material gold, but thinks that he has it returned to him symbolically in the form of the golden-haired child. Godfrey Cass is now free to marry Nancy, but continues to conceal the fact of his previous marriage—and child—from her. However, he aids Marner in caring for Eppie with occasional financial gifts. More practical help and support in bringing up the child is provided by Dolly Winthrop, a kindly neighbour of Marner's. Dolly's help and advice assist Marner not only in bringing up Eppie, but also in integrating them into village society.

Sixteen years pass, and Eppie grows up to be the pride of the village. She has a strong bond with Silas, who through her has found a place in the rural society and a purpose in life. Meanwhile, Godfrey and Nancy mourn their own childless state, after the death of their baby. Eventually, the skeleton of Dunstan Cass—still clutching Silas' gold—is found at the bottom of the stone quarry near Silas' home, and the money is duly returned to Silas. Shocked by this revelation, and coming to the realisation of his own conscience, Godfrey confesses to Nancy that Molly was his first wife and that Eppie is his child. They offer to raise her as a gentleman's daughter, but this would mean Eppie would have to forsake living with Silas. Eppie politely but firmly refuses, saying, "I can't think o' no happiness without him."