After serving 5 years in prison for embezzling church funds, Dr. Ephraim Nye returns to Ostable and the scornful gossip of its residents, led by Althea Bemis. There is a typhoid epidemic, and Dr. Nye believes it to be caused by the water in a pond that Judge Copeland, the brother of Dr. Nye's dead wife, Fanny, wishes to use as the source of municipal water supply. Only Katherine Minot supports Dr. Nye, but biologists prove him correct; and Dr. Nye confronts Copeland with proof that he went to prison to protect Fanny, the actual criminal. Copeland finally consents to the marriage of his daughter, Faith, to Tom Stone, the son of his enemy; and Katherine spreads the news of her engagement to Dr. Nye through Althea.

Elinor Shale's happiness at being engaged to Gerald Forster is interrupted by the arrival of her sister Lucy, who confesses that she will soon give birth to an illegitimate child. Elinor goes into seclusion with her sister until the baby is born and then tries to find a foster mother. Seeking to estrange Gerald from Elinor so that she may marry him herself, Lucy convinces him that Elinor is the child's mother. After Lucy and Gerald's marriage, Elinor learns of her sister's perfidy and resolves to tell Gerald the truth, but at the sight of their happiness, she relents and returns home.