Plot
Under the watchful eyes of Father Silvano Bentivoglio and Dr. Vittoria Vetra, the European Organization for Nuclear Research (CERN) initiates the Large Hadron Collider and creates three vials of antimatter particles larger than any that have ever been produced before. Immediately afterward, Father Silvano is killed and one of the vials of antimatter goes missing. Meanwhile, the Roman Catholic Church mourns the sudden death of Pope Pius XVI in Rome and prepares for the papal conclave to elect the next Pope while Camerlengo Patrick McKenna assumes temporary control of the Vatican. The Illuminati kidnap the 'preferiti' (the four most likely cardinals to be elected pope) before the conclave enters seclusion and threaten to kill one candidate every hour and destroy all of Vatican City at midnight, using the missing vial of antimatter as a bomb. The Vatican summons symbologist Robert Langdon from Harvard University and Vittoria from CERN to help them save the four preferiti and locate the vial.
Langdon listens to the Illuminati's message and deduces that the four cardinals will die at the four altars of the "Path of Illumination," marked by statues of angels in locations relevant to the four classical elements. Over Richter's objections, but with McKenna's consent, Langdon is granted access to the Vatican Secret Archives to examine Galileo Galilei's banned book, and following clues with Vittoria, Inspector General Ernesto Olivetti, and Lieutenant Valenti of the Vatican Gendarmerie Corps, arrive at Chigi Chapel in the Church of Santa Maria del Popolo. There they find Cardinal Ebner dead, suffocated with soil and branded with an ambigrammatic word "Earth". They verify the second altar's location is Saint Peter's Square, but are unable to save Cardinal Lamassé, his lungs punctured and his body branded with an ambigrammatic word, "Air".
While Vetra studies Silvano's diaries, Langdon and the Vatican officers locate the third church, Santa Maria della Vittoria, but are unable to save Cardinal Guidera from being burned to death. His body is branded with an ambigrammatic word, "Fire". The assassin appears and brutally kills everyone except Langdon, who escapes. Langdon and two Carabinieri officers race to the Water altar, the Fountain of the Four Rivers, where the assassin murders the officers and drops a bound and weighted Cardinal Baggia into the fountain. Langdon, assisted by bystanders, saves the cardinal, who tells him the Illuminati's lair is Castel Sant'Angelo. There Langdon and Vetra discover a hidden passageway leading to the Vatican, being used as a hideout for the assassin. Discovering a case with marks for five branding irons, they realize the fifth brand is for the camerlengo but are confronted by the assassin before they can alert McKenna. The assassin spares their lives, then cryptically warns them that his contractors were "men of God". He escapes but is then killed when his car explodes.
Inside the Vatican, Langdon and Vetra find Commander Richter hovering over McKenna with a gun, the Vatican symbol branded into McKenna's chest. Richter is shot by the Guards, and Langdon takes a key that slips from Richter's hand. The stolen antimatter vial is found in St. Peter's Tomb below the church, but the battery life is too low to risk re-connecting it to a battery. McKenna, a former military pilot, seizes the vial and uses an awaiting helicopter to fly above the Vatican. At a high altitude, he parachutes out as the antimatter bomb explodes overhead. McKenna is hailed a hero and savior, and the cardinals move to elect him pope. Langdon and Vetra use Richter's key to watch a security video showing McKenna speaking to Richter before the attack. The video reveals that McKenna, not the Illuminati, is the mastermind behind the scheme, intending to use the incident to be named pope and rally the church's most conservative followers to his side. This video is shown to the Papal conclave, and when McKenna discovers he has been exposed he flees to a remote recess in the building where he is able to commit suicide before anyone can stop him.
The Vatican officially announces that McKenna died due to internal injuries suffered during his parachute landing, and Cardinal Baggia is named Pope Luke I, with Cardinal Strauss as the new camerlengo. Strauss thanks Langdon for his assistance and gives Langdon Galileo's "Diagramma Veritatis" for his research, requesting only that Langdon's will contain a bequest that it be returned to the Vatican, and that any future references he makes to the Catholic Church in his future publications are done "gently". The movie closes with the newly elected pope, Cardinal Baggia, stepping out onto his balcony for the first time to the cheers of the crowd below.
