The narrator travels to Corsica in 1841 and stays at the home of the widow Savilia de Franchi. Gradually he is initiated into the family secrets and learns that the widow once gave birth to Siamese twins, who have a very close bond with each other since their lives. Nevertheless, they developed very different. While Louis practices law in Praris, Lucicen stayed in Corsica with his mother. Not only that, Lucien must mediate between two hostile families and prevent their vendettas. And the narrator is asked to accompany him on this dangerous mission...