“The Diary of a Madman” is about Aksenty Ivanovich, a titular councilor in modern Russia. Aksenty does not care for his position, though he is rather proud of his social standing. A clerk is considered a nobleman, but Aksenty expresses that his particular department is a dead end. Aksenty is walking to work when he passes a carriage that has stopped in front of a store. His boss’s daughter and her little lapdog exit the carriage. When the girl enters the shop, her dog, Medji, is left in the street. Aksenty hears somebody address the dog, and hears Medji respond. She is speaking to another little dog that was following two women walking down the street. Though startled at first, Aksenty recalls stories about other animals that could talk and brushes off the peculiar situation, until Medji proclaims that she wrote a letter to the Fidèle, the dog she was speaking to. Aksenty has never heard of a dog who could write a letter. He decides to follow Fidèle back to her house. When he sees where she lives, he resolves to go back to that house sometime and obtain the letters Medji wrote to her.
Aksenty Ivanovich reveres his boss for being intelligent, learned, and important. Aksenty also is very attracted to his boss’s daughter. When she walks into Aksenty’s office looking for her father, Aksenty is overwhelmed by her presence. She leaves and he sits in a stupor until a lackey tells him to go home. He passes by her house, hoping she will come out, but she does not appear.
Aksenty recalls the conversation between the dogs he overheard and goes to Fidèle’s building to retrieve the letters. One of the women Fidèle was following in the street opens the door and Aksenty asks to speak to her dog. The girl is confused, and Aksenty rushes into the house, finds Medji’s letters in Fidèle’s box, grabs them, and leaves.
Aksenty reads the letters. Many of them are too “doggy” for him, but he is persistent as he searches for any word about the woman he is infatuated with. He learns that her name is Sophie and she is being courted by a man named Teplov. Teplov is a kammerjunker, a high class servant to the royal family. Medji says that “Sophie loves him to distraction” and will soon marry him. Aksenty is shocked and in denial. He questions why he is a titular councilor, and what determines this. He recalls stories about peasants who were unknowingly nobleman and suddenly learn of their true status. Aksenty wishes that he would suddenly ascend social classes so he can impress Sophie.
Aksenty reads in the paper that there is chaos in Spain. The officials are trying to crown a woman as Queen, but some are saying a Queen cannot rule, there must be a king. But there is no king to take the throne. Aksenty believes there is a king; he just has to be found.
Throughout the short story Aksenty has been keeping track of the date, but suddenly records wild and impossible dates. In the same entry, Aksentry reveals that he is the missing King of Spain. He stops going to work until his manager told him to go to the office, but he only goes “as a joke.” He signs a piece of paper as “Ferdinand VIII,” and leaves. He goes to Sophia’s house, walks right in, tells her happiness awaits her, and leaves.
Aksenty waits for the Spanish deputies to come and bring him to Spain. Realizing that his clothes were not presentable enough for a king, Aksenty makes himself a royal robe by cutting up one of his uniforms. After much waiting, the Spanish deputies finally come for him and he leaves for Spain. There, the Spanish government shoves him into a little room and strikes him. Aksenty has a few revelations, such as how Spain and China are the same country, and how the earth is going to sit on the moon. The Spanish government shaves Aksenty’s head and asks him questions about his identity. They pour cold water on his head and strike him with a stick. Aksenty believes they are testing him before he can take over the throne.
In the last entry, it looks like Aksenty finally realizes that he is in an insane asylum, not Spain. He seems to realize that he is being tortured for claiming to be the King of Spain, and that he may even be aware of his madness, but the last sentence dismisses all of that when he circles back into believing he is the King of Spain.