One of the hallmarks of The Godfather film trilogy is the fact that many of its characters and plot points are inspired by real-life figures and historical events. The Godfather: Part III (1990) interweaves a fictional account of two real-life events: the 1978 death of Pope John Paul I and the Papal banking scandal of 1981-1982. 

Nearing the end of his life, Michael Corleone (Al Pacino) attempts to legitimize his criminal empire and save his soul through charitable acts. One of his latest business ventures involves a stock purchase in International Immobiliare, an international real estate holding company. Now the company's biggest shareholder, Michael offers to buy out the Vatican’s 25% share. 

Since Archbishop Gilday (Donal Donnelly), head of the Vatican Bank, has accumulated a massive deficit, he is more than willing to take Michael’s $600 million offer. However, Pope Paul VI, who is gravely ill, must approve the deal.

International Immobiliare bears a strong resemblance to Società Generale Immobiliare, an Italian real estate and construction company. Originally founded in Turin in 1862, Società Generale Immobiliare then moved to Rome in 1870. Over the years, the Vatican become the company’s largest shareholder but sold most of its shares to the American conglomerate Gulf and Western in the late 1960’s when it became involved in the Banco Ambrosiano scandal. 

Banco Ambrosiano was Italy’s second largest privatized bank when it collapsed in 1982. Headquartered in Milan, the Vatican Bank was the financial services’ biggest shareholder. Chairman Roberto Calvi, a Milan native, involved the bank in questionable dealings before he was later found hanged by his neck from the Blackfriars Bridge on the edge of the financial district of London. 

The Godfather: Part III’s Frederick Keinszig (Helmut Berger), Calvi’s fictional counterpart, meets the same grisly end. Archbishop Gilday (who shares similarities with Paul Marcinkus, an American archbishop of the Roman Catholic Church who served as the President of the Vatican Bank from 1971 to 1989) is also gunned down by Corleone associate Al Neri (Richard Bright). 

However, at the center of all this real-life and fictionalized criminal activity, is the death of Pope Paul VI and his successor, Pope John Paul I. Shortly after arriving in Sicily, Michael gives confession to Cardinal Lamberto (Raf Vallone), who at the time is favored to become the next Pope. Once the Cardinal becomes Pope, his reformist agenda is seen as a threat to the questionable activities taking place behind the scenes. Although Michael ultimately eliminates his former business partners in the Vatican, his actions cannot save the new Pope, who is later found poisoned. 

Besides the events surrounding the Papal Banking scandal, there have been many conspiracy theories in regard to what actually led to the real-life death of Pope John Paul I only 33 days after his inauguration. One of these theories claims that Albino Luciani, as he was known before the prestigious position, was murdered by the Soviet Union. Others insist that he was killed due to his intentions to reestablish the Tridentine Mass, which from 1570 to 1962 was the most widely used Mass liturgy in the world. However, this particular rite ended after the introduction of the Mass of Paul VI in 1969.