: Children's fear of a young man - fear of Sandman - comes to life, invades the adult life of a young man and destroys him.

Nathaniel writes to a friend, the brother of his bride, Lotaru. In a letter, the young man talks about his childhood fear of the Sandman coming for children who do not want to go to sleep.

As a child, Nathaniel and his sisters gathered in the evenings in the living room, and his father told them interesting stories. At nine in the evening, my mother said that the Sandman would come soon, hurriedly took the children to sleep, and soon slow, heavy steps were heard on the stairs. Nathaniel was sure that the terrible Sandman was coming to his father, although his mother denied this.

The old nanny Nathaniel said that Sandman takes his eyes from children and feeds them to his children with owl beaks, who live in a nest on the moon. After this story, Nathaniel began to suffer nightmares.

This went on for many years, but I still could not get used to this sinister ghost, and the image of a terrible sandman did not fade in my imagination.

Once Nathaniel decided to see the Sandbox and after nine in the evening he hid in his father's room. The sandbox turned out to be lawyer Koppelius, who often dined with them. He was an extremely nasty person, the children and their mother were afraid and hated him, and his father treated Coppelius with great respect.

Nathaniel was numb with fear, and the lawyer and father opened the doors of the closet, behind which there was a deep alcove with a small brazier, lit a fire and began to forge something. In a muffled voice, Coppelius ordered him to give his eyes, and Nathaniel, terrified, fell out of his hiding place.

The lawyer grabbed the boy, intending to use his eyes in his experiments, but his father begged him to spare his son. Then Coppelius began to twirl and bend the arms and legs of the child, wanting to study their mechanism. Nathaniel passed out and spent many weeks in fever.

Copellius disappeared from the city, but a year later he reappeared in Nathaniel's house and set about alchemical experiments. An explosion occurred late at night, his father died, and the police began to search for Coppelius, and he disappeared.

Shortly before writing the letter, already a student, Nathaniel saw Sandbox again - he appeared to him under the guise of a barometer seller, Piedmontese mechanic Giuseppe Coppola, but he looked very much like Coppelius. The young man decided to meet with him and avenge the death of his father.

Clara accidentally reads a letter addressed to her brother Lotaru, and tries to prove to her fiancé Nathanael that all this is just a fantasy that he takes for reality.

If there is a dark force that so hostilely and treacherously imposes the threads on our soul with which it then completely entangles us, ‹...› then it must be in us.

In a reply letter, Nathaniel chuckles at her bride’s sanity and asks her friend to stop reading her letters. Now Nathaniel is sure: Giuseppe Coppola is not at all Koppelius's lawyer. He was convinced of this by the physics professor Spalanzani, whose lectures the young man began to attend. The scientist has known Coppola for many years and is sure that he is an indigenous piedmont. Mentioned Nathaniel and the mysterious daughter of a professor, Olympia, an incredibly beautiful girl who Spalanzani hides from prying eyes.

These letters fall into the hands of the narrator. Based on them, he describes the future fate of Nathaniel. The narrator reports that after the death of his father, Nathaniel’s mother took the orphaned children of a distant relative, Lothar and Clara. Soon Lothar became the young man’s best friend, and Clara became his lover and bride. After the betrothal, Nathaniel went to study in another city, from where he wrote his letters.

After the last letter, Nathaniel interrupted his studies in science and came to the bride. Clara discovered that her lover had changed a lot - became gloomy, brooding, full of mystical forebodings.

Any person who considers himself free, in fact, serves a terrible game of dark forces, and it is useless to fight this, it is better to humblely submit to the will of fate.

Nathaniel began to write strange poems that annoyed and angered the sensible and clever Clara. The young man began to consider the bride cold and insensitive, unable to understand his poetic nature.

Nathaniel once wrote a particularly creepy poem. It frightened Clara, and the girl asked to burn him. The offended youth brought the bride to tears, for which Lothar challenged him to a duel. Clara found out about this and hastened to the place of the duel, where there was a complete reconciliation.

Nathaniel returned to his studies almost the same. Arriving, he was surprised to find that the house where he was renting an apartment burned down. Friends managed to save his belongings and rented a room for him in front of Professor Spalanzani's apartment. Nathaniel could see Olympia's room - the girl sat motionless for hours, stroking in front of her.

One evening, Coppola came back to Nathaniel and, chuckling nastyly, sold him a telescope with surprisingly good lenses. The young man looked at Olivia better and marveled at her perfection. For days he looked at Olivia, until Spalanzani ordered to curtain the windows in his daughter's room.

Soon, Spalanzani arranged a big ball, at which Nathaniel met Olivia and fell in love with a girl unconscious, forgetting about his bride. He did not notice that Olivia hardly speaks, her hands are cold, and her movements are like that of a mechanical doll, although the girl made a repulsive impression on the rest of the students. In vain Sigmund, Nathaniel's best friend, tried to reason with him - the young man did not want to listen to anything.

After the ball, the professor allowed Nathaniel to visit Olivia.

He had never had such a grateful listener. She ‹...› sat without moving, fixed a fixed look in the eyes of her lover, and this look became more and more fiery and lively.

The young man went to make an offer to Olivia when he heard a noise in the office of Spalanzani and found there a professor and terrible Coppelius. They quarreled and pulled out an immovable female figure from each other. It was an eyeless Olivia.

It turned out that Olympia was not really a man, but a machine, invented by a professor and a lawyer. Koppelius tore the doll from the professor and fled, and Spalanzani stated that Olivia's eyes had been stolen from Nathaniel. Madness took possession of the young man, and he ended up in a madhouse.

Due to the scandal, Spalancini left the university. Nathaniel recovered and returned to Clara. Soon, the Nathaniel family received a good inheritance, and the lovers decided to play a wedding.

Walking once around the city, Nathaniel and Clara decided to climb the high tower of the town hall. Looking over the neighborhood, Clara pointed out to the groom something petty, he took out the spyglass of Coppola, looked into it, and again he was seized with madness.

Suddenly streams of fire poured from his wandering eyes, he howled like a hunted beast, jumped high and, laughing loudly, screamed in a piercing voice.

Nathaniel tried to throw Clara down, but she managed to grab the railing. Lothar, waiting near the town hall, heard screams, rushed to help and managed to save his sister. In the meantime, a crowd gathered in the square, in which the insane Nathaniel noticed Coppelius, who had just returned to the city. Screaming wildly, the young man jumped down and smashed his head on the pavement, and the lawyer again disappeared.

Klara moved to a remote place, got married, gave birth to two sons, and found family happiness, "which Nathanael could never give her with his eternal spiritual discord."