The Godfather 3 begins with some decaying wood floating in the water. A dilapidated house with no one living there, and fallen leaves blown up by the wind. This sets the tone of the film — the decline of the Corleone family. "Only children in the world are treasures, and the wealth and power of the world are incomparable" Is a letter written by the elderly MacCorion to his children, inviting them to attend his canonization ceremony. In his later years, Mike was loyal to philanthropy, the Holy See awarded him the Order of St. Sabasin, and Mike announced the formal establishment of the Koebsky Foundation. Let the daughter Mary serve as honorary chair.
Vinson's boss, Zaza, approached Mike to complain about some problems with Mike's nephew Vincent's job. "Zaza often scolds the Corleone family behind his back," Vinson says, and Mike doesn't want to deal with such chores anymore and let them deal with them peacefully. Zaza cursed a dirty word in Vinson's ear, and Vincent directly bit Zaza's ear. Zaza then sent someone to assassinate Vincent, and both killers were killed by Vincent. The Archbishop of Rome, who manages the Vatican Bank, sought Mack to help them pay off $600 million in debt. Promised that he could control the stake in the real estate "Yili Group" so that Mike's mafia family business could be cleaned up. Eager to legalize the family business, Mike quickly punched the money off.
The older mafia, Aitubello, said that his old guys also wanted to take a stake in the "Yili" group. Mike said the "standing" business must be legal and no longer have ties to the mafia. Mike gathered the big guys together and had a meeting. He said that he had sold all the casinos, and everyone's cooperative business was over. Everyone got a satisfactory check based on their casino shares. Zaza, who had a lot of money and no stake in the casino, quarreled with Mike on the spot, and Zaza had the casino door secretly locked in handcuffs. Helicopters were then sent to shoot at the venue, and Mike escaped under Vincent's cover.
Mike knew that Zaza wouldn't come up with the idea of shooting him from a helicopter, and guessed that there must be someone behind him. Vincent, with the consent of his aunt Connie (Mike's sister), secretly plans to kill Zaza. Meanwhile, Mike's daughter Mary finds Vinson, and the two exchange words and have a relationship. Mack learns and tells Vincent not to be too impatient and to oppose both of them. On the other hand, the "Yili" Group was slow to agree to let Mike Hold. Mike knew it was a hoax, and he had been deceived by the Archbishop. Mike returns to Sicily to visit His Excellency Tommasino in order to find out who is behind the "Standing" group and the assassination. Tommasino told him that only black and white Rougasi had this ability. Then he introduced Mike to Cardinal Lombardo.
Mike denounced Lombardu of collusion with high-ranking politicians to embezzle money, and confessed to Lombardo. Mactan had no choice but to kill his second brother, Fredo. Returning from church, Mike says to his sister Connie, "All my life, I will strive to be upstream in society", and things that are high above are always legal and upright. In addition, Mike asks Vincent to go undercover in Aitubello to find out about the "Standing Group" and the assassination. Vinson tells Mike that all this is a trap set by Aitubello and Rugassi. On the other hand, the old pope of the Vatican died, and Lombardo was elected the new pope. Lombardo immediately dealt with the archbishop's corruption case, and the archbishop and Rugasi planned to fight to the death. They killed Lord Tommasino, and Mike was very sad to learn of it, thinking that Lord Thomasino's death was all because of him. Mike then vowed never to commit a crime again. After quitting the mafia, Mike gave the Corleone family rights to Vincent.
Mike then went to see his son Anthony's first opera performance. Aitubello arranges for the killer to blend in, intending to assassinate Mike. The new godfather Vincent arranged everything during this time. Through ingenious layout, both the Archbishop and Rugassi were eliminated. Aitubello was also poisoned to death by Mike's sister Connie. The killer fails to assassinate Mike at the end of the opera, but kills Mary. Holding his daughter's body, Mike tore his heart out this time. Vincent shot the killer.
At the end of the film, Mike returns to his hometown in Sicilia and sits alone in a chair basking in the sun. Recalling the events of the past, Mike dies in his memories.