The Murders in the Rue Morgue
Monsieur C. Auguste Dupin
Dupin is clearly the main character: he's the one who provides living evidence of the ingenious and analytical mind. The narrator spends all of his time staring at Dupin and jotting down his every word, which indicates that Dupin is important to the text. What is more, he's the one who first identifies the Ourang-Outang murderer that unknots this otherwise impossible mystery.