Auguste Dupin is a character from Edgar Allan Poe's detective fiction works. He appears for the first time in Poe’s short story "The Murders in the Rue Morgue". Dupin is an archetype of a detective character and he is the basis of all detective stories that came up in the future. Poe sets the standards for a good protagonist in detective fiction through Dupin.

A detective fiction protagonist is usually a pathological person in terms of his or her psychology. Most detectives have a mania, phobia or an addiction that results in their compulsive nature. Detectives in fiction seek pleasure in solving crimes and Dupin is no exception. Dupin is inquisitive by nature. The opening of the story describes him to be searching for an elusive text and this can be considered a metaphor for detection. Dupin searches for a hidden story and this reflects in his quest to find the murderers.

Dupin uses his intelligence to follow ratiocination. He has superior powers of deduction and reasoning. This is evident when he notices even minute details such as the way of tying a ribbon and the ability to think out of the box. In the short story "The Purloined Letter", Dupin uses his unique intelligence to find the place where the minister's letter is hidden. While the police search in the most obvious and common places, Dupin is the only one who looks for it in unusual places and ends up solving the case.

Detective fiction also portrays the interiority of the detective's mind. Dupin has a disregard for social norms and conventions. He is least bothered about the consequences of investigating on his own even though he is not a police. This shows his keenness towards crime solving, another characteristic feature of a detective in fiction. This is also seen in Sherlock Holmes.

Like every detective character, Dupin is also secluded from society. He prefers remoteness from society and enjoys being alone. This makes him a keen observer and a detail-oriented man. This is seen when Dupin finds that the window latch is defective and that it is easy for the suspect to escape. While the police overlooked the seemingly intact latch on the window, Dupin's keen eye spotted it as soon as possible. All these add to his detective nature.

A good detective is also diligent and willing to risk his life. This is found in Dupin as he is not afraid of breaking rules to solve the crime. Dupin proves his mettle as an efficient detective every single time much to the annoyance of Mr. G, the Prefect.

An efficient detective detaches himself from the emotional aspect of the scene’s violence. Like a mathematician, he views the crime scene as a site of calculation. This is seen in Dupin as he is very professional at the crime scene. Instead of being intimidated by the gruesome sight, he views it as a case and handles it with an analytical approach.

All these qualities are also found in Monsieur Lecoq. Lecoq is the main character in Emile Gaboriau's novel. He is known for his power of detailed observations. Lecoq investigates with great precision and he carefully gathers minute clues from the crime scene. This is evident when he notices the footprints of two women in the snow outside the bar where two murders have taken place.

Lecoq is also a rational thinker, which is the most important feature of a good detective. He uses his intelligence to think beyond his senior's orders. As a junior detective, though Lecoq is an amateur, he is the first one to suspect that something else is there in the case than the eyes can see.

Lecoq also shows traces of eccentric behavior and compulsiveness like Dupin or any other detective in detective fiction. Lecoq solves crimes just for the happiness he feels from solving them and in order to attain this he risks his safety. This eccentricity is also found in other detectives like Sherlock Holmes and Hercule Poirot.

Ronald Knox in his "Ten Commandments of Detective Fiction" mentions that "The detective must not light on any clues which are not instantly produced for the inspection of a reader." This is followed by both Dupin and Lecoq. Dupin suspects the murderer by analyzing the pattern of tying the ribbon and finds it to be a sailor's method. Though later it is found that an orangutan is the murderer, Poe has made Dupin immediately light on the clue of the ribbon. Similarly, Lecoq relies on the footprints on the snow to solve the mystery.

The most important feature of a detective in detective fiction is the ability to establish a strong connection with the reader. This is achieved through the first-person narrative by Poe in Dupin. In Lecoq, this is seen by the inexperienced amateur detective who struggles through the process and has to seek the help of his senior colleagues. This makes the character more realistic and relatable to the reader.

Thus, both the characters of Dupin and Lecoq prove to be typical of detective fiction. They have been established as the predecessors of good detective characters in detective fiction.

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