At a psychological conference in Chicago, Charlie becomes upset. First, having become more intelligent that either of the doctors who engineered his heightened intelligence, he realizes their data is flawed. He and Algernon will rapidly lose the intelligence they had so rapidly gained. Further, he resents being treated like a lab animal and belittled for being the handicapped person he once was by the scientists. Emotionally in a turmoil, he decides to go back to New York.
Near the end of his journal account, Charlie explains why he is now going away from New York. At this point, he has run the gamut from being mentally handicapped to becoming highly intelligent to losing his intellect. The experiment that was supposed to permanently enhance his intelligence failed because the aging Dr. Nemur rushed it along: he wanted one last success to crown his long career.
The re-mentally handicapped Charlie confides to his journal that he made a mistake. He forgot he was no longer taking Miss Kinnian's class at the adult center, so he showed up for it. This so upset Miss Kinnian, who was once in love with him, that she started to cry and ran from the room. Charlie looked around and noticed that none of the other students were familiar. He realized he didn't belong in the class and had caused a scene:
Thats why 1m going away from New York for good. I dont want to do nothing like that agen. 1 dont want Miss Kinnian to feel sorry for me. Evry body feels sorry at the factery and I dont want that eather so 1m going someplace where nobody knows that Charlie Gordon was once a genus and now he cant even reed a book or rite good.