The novel begins in 1872, after the fall of the Second Empire and the end of the reign of Emperor Napoleon III. Pascal, a physician in Plassans for 30 years, has spent his life cataloging and chronicling the lives of his family based on his theories of heredity. Pascal believes that everyone's physical and mental health and development can be classified based on the interplay between innateness (reproduction of characteristics based in difference) and heredity (reproduction based in similarity).