Nan Prince is an orphan who becomes the ward of the local general practitioner, Dr. Leslie, upon the death of her elderly aunt. Nan and Dr. Leslie develop a close emotional bond. She is a bright young woman who enjoys accompanying him during his long day's work as a country doctor in Oldfields. They often discuss medicine and healing. Dr. Leslie encourages Nan to read medical books, while instilling in her an understanding of the intimacies of his patients' lives and a love of caring for them. He would like to see her become a physician, an ambition she soon begins to pursue despite many obstacles. She goes away to medical school in the city.

After her first year at medical school, she spends part of the summer in the town of Dunport where she is introduced to her closest relative, Miss Prince (her father's sister), and the "smart" society she has never experienced in the country. Miss Prince and Nan's new friends are all amazed and scandalized by the thought of a woman becoming a physician. They think the whole idea is utterly outrageous, especially for a young, attractive woman like Nan.

She meets and falls in love with a young lawyer, George Gerry, who asks her to marry him. With great emotional pain (but no hesitation), Nan chooses medicine over marriage. She returns to medical school and, after graduation, to spend a year in Oldfields practicing with Dr. Leslie. In the end she stands by the river on a beautiful summer day, raises her hands to the sky, and exclaims, "O God . . . I thank thee for my future!"