As Charlie's intelligence grows he finally becomes smart enough to beat Algernon in the maze race
I BEAT ALGERNON!
Charlie realizes his friends bully him and gets very upset
"I ain't laughed so much since we sent him off for the newspaper that night at Muggsy's and ditched him."
"He's a scream,"
"Look at him! His face is red."
Charlie's IQ is about the same as an average person at this point. He goes to a diner and sees a dishwasher boy, about as dumb as Charlie used to be, drop a stack of plates and everyone laughed at him. Charlie then got upset and yelled at everyone.
"Shut up! Leave him alone! It's not his fault he can't understand! He can't help what he is! But for God's sake... he's still a human being!"
Algernon dies and because both he and Charlie had gone through the same experiment, Charlie wonders if what happened to Algernon may happen to him. Especially when his knowledge begins to slowly deteriorate.
Charlie buries Algernon in the backyard in a cheese box and begins losing more and more knowledge each day starting with the most recent things he had learned.
"my mind is deteriorating rapidly. I won't let it happen. I'll fight it. I can't help thinking of the boy in the restaurant, the blank expression, the silly smile, the people laughing at him. No-please-not that again..."
Charlie has returned to his original state and writes about how he is sad that he lost all his knowledge and he is moving somewhere where he will have lots of friends. He then writes down his goodbyes to everyone and tells them if they have a chance to put some flowers on Algernons grave.