If horror movies have taught us anything, it's that children who sneak up on you silently are bad news.
Okay, so the extent of this kid's negative influence might be just that he seriously stresses out an old man regarding the safety of his money bags. But he sure twists the paranoia knife further by offering free pamphlets to detect counterfeit bills: "Loose bait ain't bad," said the boy, "look a lie and find the truth; don't care about a Counterfeit Detector, do ye? or is the wind East, d'ye think?" (45, 97).
What's worth noting is that while most of the other con-type characters in the novel have to work to convince their suckers—er, customers—to buy what they're selling, this kid just walks up with his miniature door and rakes it in.
Why? Because everyone else leads by trying to garner confidence. Child of the corn over here capitalizes on natural human distrust by selling them locks and wallets. In other words, he gets money by offering people a means to keep money. Go figure.