The story begins in the United States at the beginning of the 20th Century. The Sicilian boy Vito Andolini, whose parents have been murdered by the local mafia, comes to New York and rises there under the name of his home village Corleone to the most powerful mafia godfather. When he declines to join the emerging drug trade He is gunned down in the street and a bloody war breaks out between rival Mafia families. Sonny, the eldest son, takes over responsibility for the family business for the mentally disabled godfather. When he is lured into a trap and shot dead at a tollbooth, the recovering Vito Corleone rises from the bedside to make a strategic peace that will enable his youngest son, Michael, to return from Sicily. Michael hid in Sicily after seeing the drug dealer responsible for attacking his father along with his bodyguard (a corrupt high police officer) had murdered. Michael finally takes over the family business, repulses the enemies and further expands the power of the family clan.
The first part begins with the day of the wedding of the daughter of the godfather and ends with the murder of Sollozzo. The second portrays part of the life of Johnny Fontane. The third part describes Vito Corleone's history in Sicily and New York. The fourth and fifth parts are mainly about the murder of Santino "Sonny" Corleone. The sixth part describes Michael's life in Sicily and the assassination attempt on him, the seventh his return to the United States and the death of Don Vito Corleone. In the eighth part, the bodyguard Albert "Al" Neri plays an essential role. The ninth and final part is about the relationship between Michael "Mikey" Corleone and his wife Kay.