Hitman Virgil "The Turk" Sollozzo is hired by the Tattaglia and Barzini families to kill off Don Vito Corleone, the most powerful mafia Don in New York. Vito survives the assassination, and his youngest son, Michael, launches a vendetta to kill the other four families and The Turk, and gets involved in the mafia family business which he was so hesitant to join in earlier years.

Michael Corleone adapts to a life of solitude, Sonny grapples with his sister's abuse, and Vito seeks council.

Michael manages the responsibilities of being a mafia don. Kay grows complacent with her husband's tightening of the crime syndicate, and danger looms due to a mysterious traitor.