The Godfather

Michael is a young World War II veteran and son of Don Vito Corleone, the head of the Corleone mafia family and de facto 'godfather' of the Five Families. Michael has managed to stay out of the family business, run largely by his father, his oldest brother Santino a.k.a. Sonny, and adoptive brother Tom Hagen, who is the family's counselor or consigliere. At his sister Connie's wedding to Carlo Rizzi, Michael introduces his family to his girlfriend, Kay Adams.

Approaching Christmas, Michael becomes embroiled in family affairs when Vito is gunned down by two assailants. Vito had earlier refused to offer protection to drug baron, Virgil "The Turk" Sollozzo, for dealing narcotics in the city. Sollozzo has the support of the Tattaglia family, who also take down notorious Corleone enforcer, Luca Brasi. While Vito survives the attempt and recovers at the hospital, Sonny takes over the family as acting boss. He has Michael live at the house for his protection, as a successful hit on Bruno Tattaglia leads to war between the two gangs. After Sollozzo makes another attempt on Vito's life, Michael offers to take him out permanently. A meeting is arranged at a restaurant to discuss potential business terms, where Michael shoots Sollozzo and an accompanying police officer dead. He flees the scene, seeking refuge in his family's native Sicily, to escape the ire of the NYPD and the other gangs back home. There, he becomes attracted to a local girl, Apollonia Vitelli, and marries her.

Back in New York, war has broken out between the Five Families. Amidst this, Sonny receives a distress call from Connie. En route to her house, he is ambushed and brutally murdered at a highway toll booth. With Sonny dead and his middle son, Fredo unfit to rule, the recovering Don orders an end to hostilities. He negotiates peace with Tattaglia and the other Family heads, offering a controlled drug trade and access to his political connections in exchange for an end to all vendettas, and Michael's safe return to the US. Meanwhile, Michael survives a hit in Sicily, which kills Apollonia. He returns to the US, slowly taking over the family business. He marries Kay, after promising her he will legitimize Corleone family operations in five years. To that end, Michael visits Las Vegas, to negotiate a deal with Jewish mobster, Moe Greene, under whose protection Fredo has been living. Michael offers to buy out Greene's stake in the family casinos, but not only does Moe refuse, he also taunts Michael claiming he has support from Barzini. Upset, Michael reprimands Fredo for defending Greene.

Since the peace meeting, Vito has suspected that Barzini, not Tattaglia, is the mastermind behind Sonny's death. He and Michael discuss a potential Corleone family traitor, who might approach Michael with an offer. Vito passes away peacefully, while playing with his grandson, Michael's son Anthony. At his funeral, powerful Corleone caporegime, Tessio, asks Michael to meet with Barzini, signalling his betrayal. The meeting is set for the day of the baptism of Connie's son. As Michael stands in church to be anointed his nephew's godfather, his hitmen carry out orders to simultaneously assassinate Barzini, Tattaglia, Greene, and the heads of the other Families. Tessio, who switched sides before Vito's death, is led off to be murdered. After the baptism, Michael has Clemenza garrote Carlo, for conspiring with Barzini to kill Sonny.

At their house, Connie accuses Michael of making her a widow and her newborn son an orphan. To Kay's relief, Michael denies the accusation, but as she exits the room to prepare a drink, Corleone family capos approach Michael and offer him their allegiance. As Kay looks on with trepidation, Clemenza kisses Michael's hand and addresses him as "Don Corleone".