The young man in "Dusk" is an expert at playing on the human emotions. He tests Gortsby's ability to show compassion for his situation. The young man tells a sad story, and it would have worked had he produced a bar of soap to confirm his story. When the bar of soap is found, then Gortsby literally runs after the young man to help him in his financial situation. Even though Gorstby considers himself cynical, he fell for the young man's sob story. Indeed, the young man is well trained in playing with people's emotions. Using a really sad story worked, eventually, on Gortsby.
Likewise, the astrologer begins to share insights that play on the client's emotions. He begins to talk about how he had been stabbed. This brings up the visual image for the stranger. He is experiencing the pain and humiliation of the time he was stabbed years ago. Indeed, the astrologer too is an expert on playing on the stranger's emotions. The astrologer went right for the client's weak spot--his emotions.
Although it took a while for both the young man and the astrologer to win with the emotional story telling, ultimately, each wins over his audience by telling a really sad story. Both Gortsby and the astrologer's stranger are gullible. Each fell for a sad story which played on the emotions. Neither man had his emotions in check, even though both appeared to be cynical in the beginning. Both lost money foolishly.