The first season of this limited drama series follows the early years of young, American-born Pius XIII's (Jude Law) pontificate. Pius XIII, who was born Lenny Belardo, quickly demonstrates that he will not be a mere figurehead for the Vatican, as the Vatican Secretary of State, Cardinal Voiello (Silvio Orlando), was hoping for. Instead, Pius XIII is arrogant, self-serving, and power hungry. He publicly criticizes and questions his people's devotion to God, but the people around him begin to wonder if he even believes in God himself. Diane Keaton stars as Sister Mary, an American nun who took in Lenny Belardo when he was a 7-year-old orphan and now acts as his key advisor.