This is the story of John Trapani Jr., a young man who was a boy, who witnessed the gruesome murder of his father as ordered by Don Emilio Barzini, head of the infamous Barzini Crime Family of New York City.
He was comforted by his father's employer and good friend of the family (crime family), Don Vito Corleone who assured the boy when the time is right' when he is old enough, he would take his revenge.
Now nine years have past since the tragedy. At the age of twenty, he has long since dropped out of school, and has gotten in trouble with the law. To straightened him out he was sent to train in arm forces and saw action. Seeing that he was Sicilian and spoke it fluently. He was sent to with the Allied unit to help in liberating Sicily for which he didn't know that he was helping the Mafia in doing so. This was the first time he help with organized crime.
He returned with his two friends Harry Gardinco and Richie Valentino whom considers getting work in organized crime, but Johnny wanted no part of it considering getting his own job and living his own life outside of the Mafia, but was already mixed up with a street gang who had been doing petty crimes. His mother, Sarafina has gone to ask the don for help during his daughter's wedding. He recruits feared Corleone enforcer/senior soldeto (soldier) Luca Brasi, and shows him the ways of the Mafia. Through him, he make collections go on reconnaissance missions such as spying against another crime family, the Tattaglias, who are pushing their narcotics business from Brooklyn, to Corleone turf which started from Little Italy which stretches down to the northern end of Wall Street to the southern end of Midtown in Manhattan. On December 22, 1945, the don is gunned down by two Tattaglia soldiers and John rushed him to the hospital with the don's weak-willed son Fredo on tow.
Johnny is made enforcer after learning the demise of Brasi, and carries out several task for the Corleones as makes his way through the ranks of the family to become a made man to becoming under boss of the family, while the new head, Michael, expands it into Las Vegas while Johnny begins to expand all throughout New York and New Jersey to make the Corleones the most powerful family in the United States.