Cardinal Lamberto

Lamberto is a Sicilian clergyman and he is the cardinal in the Roman Catholic Church favoured to succeed Pope Paul VI. He is visited by Don Michael Corleone on the advice of the elderly Sicilian Mafia boss Don Tommasino (Michael's Sicilian ally and his father's before him). Michael tells him of the swindle at the hands of corrupt Vatican bank officials Frederick Keinszig, Licio Lucchesi, and Archbishop Gilday. Michael suddenly suffers a low blood sugar episode due to his diabetes, and Lamberto orders that orange juice and candy bars be brought to him immediately. As Michael quickly recovers, Lamberto seizes the opportunity to encourage Michael to confess his sins; initially reluctant, Michael eventually does so under the Cardinal's gentle prodding, breaking down in tears when confessing to ordering the murder of his brother Fredo 20 years before. Lamberto tells Michael that he deserves to suffer for his terrible sins, yet absolves him and tells him he still has a chance for redemption.

Upon the death of Paul VI, Lamberto is elected the new pontiff; he takes the name John Paul I upon his accession. A moral, thoroughly honest man, he immediately calls for an investigation into the activities of the Vatican Bank and requests a meeting with Keinszig, the Bank's chief accountant. However, Keinszig has left Rome with a large sum of money and several documents. Fearing that their corruption will be exposed, Keinszig, Lucchesi, and Gilday plot to murder the Pope. Gilday poisons the pontiff's tea, killing him in his sleep.