Elena Ferrante’s Neapolitan novels, which have sold 2 million copies worldwide and will debut as an HBO series on Sunday, have won praise as a sensitive portrait of female friendship, but they’re also a modern historical epic, beginning in the 1950s and spanning 60 years. And though its protagonists are the friends Elena and Lila, another group of characters shapes their home of Naples, Italy, and their lives: the Camorra, a shadowy organized crime group that gradually rises to control Neapolitan business, politics and people. In real life, the Camorra — Naples’ version of the mafia, a term that technically only refers to organized crime groups in Sicily — has a history going back centuries, says John Dickie, a Professor of Italian Studies at University College London and the author of Mafia Republic and Blood Brotherhoods, which tell the story of Italy’s organized crime networks. “The modern Camorra has its roots in Southern Italy’s prison system in the 1800s,” he tells TIME.