In chapter 5 of Avi's The Man Who Was Poe, Edgar Allan Poe, calling himself Mr. Dupin, sends Edmund out on a most interesting errand. Mr. Dupin sends Edmund to the nearest clothier to "determine the price of a coat" suitable for Edmund (52).
One reason Dupin sends Edmund on this errand is because he wants a moment alone to speak with the night watchman, Mr. Throck, who Dupin knows is somehow involved in the mystery. What happens in the store serves as a vital clue for Dupin. While Edmund is in the store, a man described as being "portly" and having a "florid face, pink lips, and great whiskers" was being fitted for a coat (56). When the portly man sees Edmund's reflection in the mirror, he begins acting very strangely. He is described as panicking and rushing out of the store. At first, he hails a cab but changes his mind and runs down the foggy street.
Later, at a party held by Mrs. Whitman, Dupin, now going by the name of Poe, meets a man going by the name of Mr. Arnold. At the party, Poe relays his story of a man ordering a "coat, a fine coat" at a clothier and rushing out without paying for it because of some unknown fear; Poe then observes as Mr. Arnold turns quite red in the face and unexpectedly leaves the party without giving any excuse except "urgent business" (118). It's at this moment Poe is able to piece together that Mr. Arnold is really Edmund's stepfather Mr. Ratchett, who stole Edmund's mother's money, left for America, and has now stolen gold with the purpose of being able to court the wealthy Mrs. Whitman. Seeing Edmund appear in the clothing shop rattled Mr. Ratchett so much that he rushed off without paying for his coat.