The film’s story begins after April 2, 2005, the date on which the death of Pope John Paul II shocked the Catholic world. The story follows Father Joseph Murolo, who was born in the United States and summoned by the Vatican to conduct an investigation into the life of the Supreme Pontiff. As the devil’s advocate (advocatus diaboli), Murolo must ensure that nothing compromises the canonization of Karol Wojtyla, the first non-Italian pope in 450 years. As he interviews various witnesses—from devout colleagues to secret confidants—Murolo sinks deeper and deeper into a moral labyrinth. This journey toward the truth will ultimately test his own faith.