The Godfather

Michael Corleone is a World War II veteran and the youngest son of Don Vito Corleone, the head of the Corleone mafia family and de facto 'godfather' of the Five Families–with the heads of the other four families being Philip Tattaglia, Emilio Barzini, Carmine Cuneo, and Victor Stracci. 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 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 garrote notorious Corleone enforcer Luca Brasi when he attempts to become a mole in Sollozzo's operation. 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 Tattaglia's son Bruno leads to war between the two gangs. NYPD Captain McCluskey arrests Vito's bodyguards to allow Sollozzo to make another attempt on Vito's life, which is stopped by Michael and Hagen. Michael arranges a meeting with Sollozzo and McCluskey, allowing Michael to shoot both men dead with a gun smuggled in by Corleone caporegime Peter Clemenza. Michael flees the scene, seeking refuge in his family's native Sicily, to escape the ire of NYPD and the other gangs back home. There, he falls in love with a local woman, Apollonia Vitelli, and marries her.

Back in New York, war has broken out between the Five Families. Sonny receives a distress call from Connie, who is being abused by Carlo. En route to her house, he is ambushed and murdered at a highway toll booth. With Sonny dead and his middle son Fredo unfit to rule, the recovering Vito orders an end to hostilities. He negotiates peace with 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 and promises that he will legitimize Corleone family operations in five years. 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 Greene refuses and flaunts his support from Barzini. After Moe leaves, Michael reprimands Fredo for defending Greene.

Since the peace meeting, Vito suspects 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 to make a deal with the Barzinis. Vito dies of a heart attack while playing with his grandson, Michael's son Anthony. At his funeral, Corleone caporegime Salvatore Tessio asks Michael to meet with Barzini, signaling his betrayal. Michael attends his nephew's baptism to be anointed as his godfather; during this, Michael's hitmen carry out orders to simultaneously assassinate the heads of the other Families as well as Greene. Tessio is led off to be executed for his treachery. Michael orders Clemenza to garrote Carlo for abusing Connie and conspiring with Barzini to kill Sonny.

At their house, Connie accuses Michael of killing Carlo. To Kay's relief, Michael denies the accusation, but as she exits the room, 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".