: A mentally retarded person has an operation to increase intelligence. He becomes a genius, but the effect of the operation is short: the hero loses his mind and finds himself in a shelter.

The narration is conducted in the first person and is composed of reports written by the main character.

The 32-year-old mentally retarded Charlie Gordon lives in New York and works as a janitor in a private bakery where his uncle took him. He hardly remembers his parents and younger sister. Charlie goes to a special school, where teacher Alice Kinnian teaches him to read and write.

One day, Miss Kinnian brings him to Professor Nemour and Dr. Strauss. They are conducting an intelligence experiment, and they need a volunteer. Miss Kinnian proposes the candidacy of Charlie, the most capable student of her group. Charlie since childhood dreams of becoming smart and willingly agrees, although the experiment involves a risky operation. The psychiatrist and neurosurgeon Strauss tells him to write down his thoughts and feelings in the form of reports. Charlie's first reports are full of mistakes.

Charlie begins to pass standard psychological tests, but he does not succeed. Charlie is afraid she will not fit the professor. Gordon meets the mouse Algernon, who has already had surgery. The experimental race goes through the maze, and Algernon is faster every time.

On March 7th, Charlie is undergoing surgery. For a while nothing happens. He continues to work in the bakery and no longer believes that he will become smart. Bakery workers mock Charlie, but he does not understand anything, and laughs with those whom he considers friends. He does not tell anyone about the operation, and every day he goes to the laboratory to do tests. March 29 Charlie for the first time passes the maze faster than Algernon. Miss Kinnian begins to deal with him individually.

On April 1, bakery workers decide to play a trick on Charlie and force him to turn on the dough mixer. Suddenly, Charlie succeeds, and the owner promotes him. Gradually, Charlie begins to realize that for "friends" he is just a clown, over whom you can make fun and evil with impunity.

I have reached a new level of development. But anger and suspicion were the first feelings that I experienced for the world around me.

He recalls the most offensive cases, becomes hardened and ceases to trust people. Dr. Strauss conducts psychotherapy sessions with Charlie. Although Gordon’s intelligence is increasing, he knows very little about himself and emotionally still remains a child.

Charlie's past, previously hidden from him, begins to clear up.

I look like a man who slept half his life and is now trying to find out who he was while he was sleeping.

By the end of April, Charlie is changing so much that the bakery workers are beginning to treat him suspiciously and hostilely. Charlie recalls his mother. She did not want to admit that her son was born mentally retarded, beat a boy, forced to study in a regular school. Charlie's father tried unsuccessfully to protect his son.

Charlie is in love with his former teacher Alice Kinnian. She's not at all as old as Charlie seemed before the operation. Alice is younger than him, and he begins inept courtship. The thought of a relationship with a woman terrifies Charlie. This is due to the mother, who was afraid that her mentally retarded son would cause harm to her younger sister. She drove the boy into the head that women should not be touched. Charlie has changed, but the ban, which is stuck in the subconscious, is still in effect.

Charlie notices that the bakery's chief cook is robbing the owner. Charlie warns him, threatening to tell the owner, theft stops, but the relationship deteriorates completely. This is the first important decision Charlie made on her own. He learns to trust himself. Charlie pushes Alice to make a decision.He confesses his love to her, but she understands that the time for such a relationship has not yet come.

The owner of the bakery was a friend of his uncle, promised to take care of Charlie and fulfilled his promise. However, Charlie has now strangely changed, the workers are afraid of him and are threatening to quit if Charlie stays. The owner asks him to leave. Charlie is trying to talk with former friends, but they hate the fool who suddenly became smarter than all of them.

Reason drove a wedge between me and everyone I knew and loved, drove me out of the house. I have never felt so alone.

Charlie has not been working for two weeks. He tries to escape from loneliness in the arms of Alice, but nothing comes of them. Gordon seems to see himself and Alice from the outside, through the eyes of the former Charlie, who is horrified and does not allow them to finally get close. Gordon recalls how his sister hated and was ashamed of him.

Charlie is getting smarter. Soon, others cease to understand him. Because of this, he quarrels with Alice - she feels next to him a complete fool. Charlie moves away from everyone he knew, and immerses himself in school.

On June 10, Professor Nemour and Dr. Strauss fly to the medical symposium in Chicago. The main "exhibits" at this major event will be Charlie and mouse Algernon. On the plane, Charlie recalls how his mother tried unsuccessfully to cure him, to make him smarter. She spent almost all the family savings that her father, the seller of hairdressing equipment, wanted to open his own hairdresser. Mother left Charlie alone, having given birth again and proving that she is able to have healthy children. Charlie dreamed of becoming a normal person, so that his mother finally fell in love with him.

Every day I learn something new about myself, and memories that began with a small ripple sweep me over a ten-point storm.

At the symposium, Charlie discovers such vast knowledge and high intelligence that professors and academics turn pale against his background. This does not stop Professor Nemur from calling him "his creation" equating Charlie with mouse Algernon. The professor is sure that before the operation, Charlie was an “empty shell” and did not exist as a person. Many consider Charlie arrogant and intolerant, but he simply can not find his place in life. In a report on intelligence-enhancing surgery, Gordon feels like an experimental animal. In protest, he releases Algernon from his cage, then first finds him and flies home.

In New York, Gordon sees a newspaper with a photograph of his mother and sister. He recalls how his mother forced his father to take him to a shelter. After the birth of a healthy daughter, the mentally retarded son aroused in her only disgust.

Charlie rents a four-room furnished apartment near the library. In one of the rooms, he arranges a three-dimensional maze for Algernon. Charlie does not even report her whereabouts to Alice Kinnigan. Soon he met a neighbor - a free artist. To get rid of loneliness and make sure of his ability to be with a woman, Charlie enters into a relationship with a neighbor. The former Charlie does not interfere with the relationship, since this woman is indifferent to him, he only watches what is happening from the side.

Charlie finds a father who divorced his wife and opened a hairdresser in a poor neighborhood. He does not recognize the son, and he does not dare to open. Gordon discovers that after drinking heavily, he turns into a mentally retarded Charlie. Alcohol releases his subconscious, which still has not caught up with the rapidly growing IQ.

Nothing in us disappears without a trace. The operation covered Charlie with a thin layer of culture and education, but he remained. He looks and waits.

Now Charlie is trying not to get drunk. He walks for a long time, enters a cafe. One day he sees a waiter, a mentally retarded guy, drop a tray of plates, and visitors begin to make fun of him.

It is amazing how people of high moral principles ...never allowing themselves to take advantage of a man born without arms, legs or eyes ... easily and thoughtlessly make fun of a man born without reason.

This encourages Gordon to continue his scientific work in order to benefit such people. Having made a decision, he meets with Alice. He explains that he loves her, but between them stands a little boy Charlie, who is afraid of women because his mother beat him.

Charlie begins to work in the laboratory. He does not have time for a mistress, and she leaves him. Algernon begins strange attacks of aggression. At times, he cannot go through his maze. Charlie takes the mouse to the lab. He asks Professor Nemour what they were going to do with him in case of failure. It turned out that Charlie was assigned a place in the state social school and hospital "Warren". Gordon visits this place to know what awaits him.

Algernon is getting worse, he refuses food. Charlie reaches the peak of mental activity.

As if all the knowledge I had acquired in recent months had come together and lifted me to the pinnacle of light and understanding.

On August 26, Gordon finds a mistake in the calculations of Professor Nemour. Charlie realizes that he will soon begin mental regression, the same as that of Algernon. September 15th Algernon dies. Charlie buries him in the backyard. September 22 Gordon visits his mother and sister. He discovers that his mother has senility. Sister is hard with her, she is glad that Charlie found them. The sister did not suspect that her mother got rid of Charlie for her sake. Gordon promises to help them as long as he can.

Gordon's IQ is rapidly declining, he is becoming forgetful. Books, previously beloved, are now incomprehensible to him. Alice comes to Gordon. This time, the former Charlie does not impede their love. She stays for several weeks, caring for Charlie. Soon, he banishes Alice - she reminds him of abilities that cannot be returned. In the reports that Charlie still writes, there are more and more errors. In the end, they become the same as before the operation.

November 20, Charlie returns to the bakery. Workers who used to mock him now patronize and protect him. However, Charlie still remembers being smart. He does not want to be spared, and goes to Warren. He writes a farewell letter to Miss Kinnian, asking him to put flowers on Algernon’s grave.