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.