This is a historical romance book. Sylvestre Bonnard, a member of the Institute, is a historian and philologist, gifted with great erudition. He lives among books, and launches himself into the research, in Sicily and Paris, of the precious manuscript of the Golden Legend, which he finally obtains. By chance he meets a young girl named Jeanne, the daughter of a woman he once loved. To protect the child from her abusive guardian Maitre Mouche, he takes her away, and she ends up marrying Henri Gelis, one of Bonnard's students.