Christopher Booker is a scholar who wrote that every story falls into one of seven basic plot structures: Overcoming the Monster, Rags to Riches, the Quest, Voyage and Return, Comedy, Tragedy, and Rebirth. Shmoop explores which of these structures fits this story like Cinderella’s slipper.
Plot Type : Voyage and Return
Voyage and Return
"Anticipation Stage and 'fall' into the other world."
In this case, we're talking about a sort of voyage and return in reverse: the hero starts the book under the spell of the State, and gradually escapes it into a health emotional state, only to fall back under the "spell" at the very end. It starts with the Anticipation stage, where the local D-503 is first distracted and then compelled by I-330 to do some very bad things (like growing as soul.) We see the first stages of his mathematical detachment breaking down in this stage, as what he perceives to be a perfect world starts to crumble.
Initial fascination or Dream Stage
This one kind of spills over into the last one, as I-330 draws him further and further into her world. It starts with the Ancient House and their visit there, leading to the slow reveal of MEPHIS and their ultimate plot to stick it to the ultimate Man. In it, we see D-503 resist falling for I-330, but prove unable to shake his fascination with her. Her, and the "irrational number" that she represents. Again, note that it's kind of taking place in reverse: I-330 breaks the soulless stranglehold over D-503, but from his perspective, she is corrupting him with her "dangerous" ideas.
Frustration Stage
Now D-503 can no longer deny his human emotions, and as he embraces them, he finds himself capable of wondrous things. He goes beyond the Glass Wall and sees the people on the other side. He schemes with MEPHIS to alter the specifics of the Integral's first flight, and helps O-90 get pregnant against the wishes of the State. With those decisions come bigger challenges, as his defiance of the Stat makes him a bigger potential target.
Nightmare Stage
When things go wrong in worlds like this, they really go wrong. In the framework of our "reverse voyage," D-503 now finds his new freedom threatened by the very forces he used to embrace. He's still kind of on the fence about it—he can be a serious wet noodle sometimes—but when push comes to shove, he always sides with I-330 and her cause. He even stays behind when O-90 flees the city, facing the Operation and possibly death rather than betray the cause.
Thrilling Escape and Return
The finale arrives, and again, we're looking at it in reverse. The Operation pulls D-503 back into the stupor that he started in: eternally loyal to the State and doing everything in his blank, monotonous power to further its goals. "Normality" of a sort is restored… though a bit of the Dream Stage has snuck back out, and continues its ongoing assault against that very "Normality" even as the novel comes to a close.