First lines: "I believe in America." That's because, in so many ways, this story encompasses so many aspects of America: the story of immigrants who came from nothing to positions of power; the story of haves and have-nots, the haves taking what they have through the use of force; the story of family, both biological and adopted; and the story of capitalism being a higher power than a professed belief and fear of God.
In the end, this is a study of power, and the transference of power from a father to his reluctant son. The idea of power, and its fluidity, attend every single scene in the film. Coppola was so popular and acclaimed in the 1970's primarily, I would argue, because he was brilliant at distilling a film's essence and infusing it into every scene. APOCALYPSE NOW: "War is not hell, war is insanity." THE CONVERSATION: "There is no such thing as privacy in the modern world."
Vito Corleone has power, Bonasera does not. So Vito flexes his muscles, invokes social code to get Bonasera to see things his way. And he refuses him. What's more powerful than telling someone no?
These backroom scenes, darkly lit, claustrophobic, contrast remarkably with the bright, musical, colorful, open, loud party outside. Here we see the rest of the family: Sonny, the hothead. Tom, the diplomat. Fredo, the idiot. Michael, the prodigal. Michael is set apart from the rest through dialogue ("Where's Michael? We're not taking a picture without Michael."), through dress (he's in a war hero's uniform, fresh from the battlefield), and he has a pretty blonde WASP with him, in contrast to the rest of the dark-haired Italian women.
Kay Adams functions as a way for the audience to make sense of this confusing world. Michael gets to describe how things work to her, and, more importantly, insist that he is different, that he is a "civilian": "It's my family, Kay, it's not me". This is the key to the film, because, above all, the movie tracks Michael's transition from being a witness to the brutality of the mob, to a participant, to the leader.
Johnny Fontaine, seemingly successful, in truth has little power. He uses his charms to gain some from Vito for a later favor. This sets up the next sequence, which is Tom in LA. Again, a power struggle: the producer showing off his enormous house, his wealth, his way with women, his prize horses. He shows off the horse as an example of that power, a great setup, which is paid off with the horse's head in his bed. His power is gone because the mob has threatened him, killing the thing he loves and entering his personal space. He has no choice but to relent -- he can't refuse, as the saying goes.
The main plot of the movie begins, and it is this: The Turk wants to partner with Vito on bringing heroin into their portfolio of criminal enterprises. Vito is stuck in the old ways, doesn't want to get involved. Again, the power of saying no, of refusing. And so, The Turk begins a war: he kills Vito's man, Brasi, and attempts an assassination on Vito himself.
Michael, still unsure of his part in all this, visits his father, who is alone (powerless). Michael arranges to move his father, understands the threat, and enlists a baker to pose as a gunman/bodyguard when assassins roll by. They exercise power through potential violence.
A cop comes by and beats Michael. This whole sequence is the turning point for the movie. Michael sees his dad in a vulnerable state and, because of his love, must act. The only way to act is to become more involved in the family. In addition, his beating at the hands of the police lead him to seek revenge, that is, to murder both the cop and their main rival. He offers to do so, which sets up the second act climax: the murder.
Michael offers to kill the cop and The Turk. He is given a gun. He is given a location. The tension builds because of dramatic irony, of our concern for the character, of the setup which leaves us wanting a payoff, of the reversals deliberate suspense (Michael reaching behind the toilet, etc.). Finally, he kills the two men and walks out, never the same again.
Midpont: the mob war continues. As always with midpoints, there's a montage or a change of scenery, a breather. In this case, we get George Lucas' B&W photos of gunned-down mobsters, and Michael in hiding in Sicily. And Vito returns home from the hospital.
Michael meets and marries Appolonia, does so by acting like a mobster -- his power over the girl's father is diminished, so he reestablishes it by giving the man his confidence about his identity.
Meanwhile, Sonny is still in charge, discovers his brother-in-law is beating his sister, and he humiliates him in another display of power. Because of this, and because of his being shut out of the family business, Carlo turns sides and sets up Sonny, who is gunned down in a serious switcheroo.
Like Michael was in protecting him, Vito is called into action by his family being threatened, a primal concern. Unlike Michael, who was spurned to kill by a threat, Vito is spurned to call a truce: "This war stops now."
Michael's identity is no longer safe, and Appolonia is killed. The feud is finally in Italy, and Michael must leave.
Michael sees Kay, he's fully Mobbed up now (he's wearing a gangster's suit and he's wearing a hat). He now justifies his father's behavior to her instead of begging off, and insists that they are going to go legit.
Changing of the guard: Michael is now the head, Tom is out, Vito is not the counseliere, they are expanding to Nevada, and the other two captains can splinter off in due time if they desire.
Vegas. Fredo throws his weight around -- he's always been the loser brother, and in an attempt to show his power in this new locale, he gets girls and a party for Michael. This won't do. Michael, now the head, was never interested in such things, but as the Godfather, he has to present the right public face. He has Fredo get the girls out (delegating the job like a boss does), calls in his favor with Johnny Fontaine, and offers to buy out Mo Greene, the casino and hotel's owner. He is all business.
Vito reveals what we knew all along -- he never intended Michael to be in the mob, expected more of him, a senator, a governor. And with that revelation, Vito can now die, and does so, with his grandson at his side.
The amazing set piece of the baptism and the murder montage is legendary for a reason: it brings back the duality we saw before, it solidifies Michael's grasp of power, gives him an alibi for the murders, is a perfect joining of the two families (mob family and biological family), is the payoff for the previous setup about the power-grab (thus also touching on the main theme).
Carlo is killed due to his betrayal. Shock: we didn't expect this.
The movie ends on a note of transition -- the family is packing up to leave New York for Nevada, and Michael lies to his wife about his role in it. What Vito tried to present comes true: Michael is now The Godfather, with no looking back.