Charlie was born with a mental illness making him unable to do some things, normal people could do. Despite his mental illness, he inspires to be smart like everyone else.
Falling Action
Charlie was given a chance to be smarter through an opportunity Mr. Strauss had offered to Ms. Kinian, which she accepted without permission from Charlie. After some tests Charlies was chosen for the operation, given the fact of his effort to be smarter. 
Falling Action
Charlies had the operation which made him smarter, reaching to an IQ over 160. Charlie got so smart that he was able to solve problems quickly, remember a lot of what he read, and understand multiple topics.
Resolution
Charlie began losing his intelligence some time later. He started noticing that he was forgetting things and losing his ability to understand things.
Charlie was desperately finding a way to not lose his intelligence but he soon understood that it was inevitable. 
Charlie loss his intelligence and everybody felt sorry for him.  Charlie decided that he didn't want people to feel sorry for him, so he left New York in search for a new place.