The Young Pope opens on the newly elected Pope Pius XIII (Jude Law), formerly known as Lenny Belardo. who at the age of 47 is the youngest man and first American ever to ascend to the highest position in the Catholic Church.
He butts heads with Vatican Secretary of State Angelo Voiello (Silvio Orlando) as he tries to maintain the order of the papacy, and both sides are willing to resort to extremes for the sake of their visions of the Catholic Church.
Cardinal Michael Spencer (James Cromwell) is a wild card after losing the papacy to his former pupil, and confessor Don Tommaso (Marcello Romolo) is conflicted between his vows and his duties to his new Holy Father.
He is an unconventional pope who was elected for reasons far more contemporary than his piety, and the cardinals who elected him soon discover that he is not going to be as cooperative as they had believed when he brings in his friend Sister Mary (Diane Keaton) to serve as an advisor.