Pierre Lacenaire, a thief and murderer, is hanged on January 9, 1836. He delivers Allard his life narrative, penned while awaiting execution. He also begs Allard to care for Hermine, whom he's guardian for over a decade. In flashbacks, we see Lacenaire's childhood as he stands up to bullies, including priests, his youthful stealing, his first murder, his brief army career, his seduction of a princess, and his affair with Avril, a young man who dies beside him.