If you are looking for a literary figure named Dupin, I tagged your question with Poe and one of his short stories entitled "The Purloined Letter." Edgar Allan Poe, while known for his Gothic contributions to American Literature, is also famous for creating the modern detective story (stories which feature an intelligent civilian who solves crime through logic and paying attention to detail all while outwitting the police).
Poe created a reoccurring character named C. Auguste Dupin. He is a wealthy Frenchman who enjoys analyzing various crimes in the comfort of his library, while the police lag several steps behind in their investigation. In "The Purloined Letter," Dupin discovers where a very important letter is being hidden by a thief and prevents far-reaching political consequences from taking place.
Poe's Dupin served as an inspiration for Sir Arthur Conan Doyle's Sherlock Holmes character, even though many readers think it is the other way around since Poe's detective stories are not as popular as his Gothic ones.