History is made when Lenny Belardo (Jude Law) becomes the fictional Pope Pius XIII, the youngest pope in history and the first American to take the reins. Having claimed the crown, he's determined to rule with an iron fist and wage a war on non-believers. His views are extremely conservative, but he harbors compassion towards the poor and underprivileged. The complex pope is stubborn and indifferent to the significance of his authority.
Sister Mary (Diane Keaton) is an American nun currently living in the Vatican under Pope Pius' rule. The pair share a mysterious, storied past that gets dredged up as he takes the papacy.