Zola designed the Rougon-Macquart novels to demonstrate how heredity and environment operate on the members of one family over the course of the Second French Empire. In this case, the environment is the department store.
Octave Mouret is introduced briefly in La fortune des Rougon. He plays a larger but background role in La conquête de Plassans, which focuses on his parents, the first cousins Marthe Rougon and François Mouret. As an innovator and risk-taker, Octave combines his mother's imagination with his father's business sense, making the department store the perfect milieu for his natural gifts. He also inherits from his great-grandmother (Adelaïde Fouque or Tante Dide) a touch of obsessive-compulsive disorder, manifested in his intense commercial drive and his obsession with dominating female consumers.
Octave's brother is the priest Serge (La faute de l'Abbé Mouret), who served as a guardian to their mentally challenged sister Desirée.
In Le docteur Pascal, the final novel in the series set in 1872-1873, Octave and Denise are married and have two children. Octave also appears briefly or is mentioned in La joie de vivre and L'œuvre.