In the first narrative thread, set in the early 1900s, a young Vito Corleone grows up in Sicily and emigrates to the United States after his family is murdered by a local mob boss. He settles in the New York City neighborhood of Little Italy, where he starts a family and begins to establish himself by helping his community, providing protection and favors. Over time, Vito's influence expands as he builds his own crime family, gaining power by carefully maneuvering within the underworld and beginning his ascent to becoming a respected and feared mafia don.

The second narrative thread follows Michael Corleone in the 1950s as he reigns as the new Don following the events that led to his rise to power. Working to expand the family business into Las Vegas, Hollywood, and Cuba, Michael faces betrayals and threats from within his own circle, including challenges to his leadership and attempts on his life. Simultaneously, he struggles with issues of trust and loyalty as he tries to secure his family's future while navigating the complex and sometimes treacherous terrain of organized crime, all the while dealing with the personal toll the life takes on his soul and relationships.