First, Charlie was stupid, when he took the first interview. But he was selected to be the one for the therapy and surgery.
He met amazing people that would help him become smarter and better. Professor, Alice, Strouse
Charlie Gets Closer to Alice
To test his intelligence, he was assigned to do a maze that he was to complete. His mission was to finish it before the mice. In the beginning, he always failed. So they decided to give him surgery.
Flowers For Algernon
Charlie was recovering from his surgery and even then he started to become smarter and smarter
As Charlie gets smarter and smarter, He also gets closer to Alice. They become more than friends. Also, Charlie after the surgery, beats Algernon, a mouse, on the maze. As time passes, Algernon starts to get weaker and weaker and quits eating.
As more time passes, Charlie realizes that he doesn't like being smart anymore. HIs friends left him, he lost his job and people even at therapy treat him different. Algernon kept getting worse and worse, and finally, he dies. Charlie was very heartbroken. He too was getting dumber and dumber and soon he started to be as he was before. That was the end of the story.