Saki devotes considerable attention to describing one section of the city at dusk.
The scene pleased Gortsby and harmonized with his present mood. Dusk, to his mind, was the hour of the defeated.
But it is not only the defeated who come out in the evening. The darkness makes it easier for con men to operate. After all, what they are doing is against the law, and they can get arrested for misdemeanors such as vagrancy and panhandling. The laws in England in Saki's day were undoubtedly much more strictly enforced than such laws are enforced in modern America. The streets were patrolled by uniformed officers, and these men would be on the lookout for law breakers.
It would appear that both the men Gortsby encounters while sitting on the park bench are con artists who happen to be working exactly the same scam. The elderly gentleman probably has more experience and hence has provided a tangible bar of soap to substantiate his story when he tells it. He drops the soap near the bench and then comes back to retrieve it, giving him an excuse to start a conversation with Gortsby, as he actually does in the story.
"Have you lost anything, sir?"
"Yes, sir, a cake of soap."
Is it too much of a coincidence that both con men should approach the same person on the same bench and tell him the same story? Gortsby probably looks like a good mark because he is well dressed and seems approachable. His meditations as he surveys the passing parade of humanity suggests a certain kind of unguarded and vulnerable body language. The fact that both predators have the same story might only mean that this is the story that is going the rounds among their colleagues. Nowadays, the most common stories we hear from minor con men are either that they need money to make a phone call or that they have run out of gas and need to buy just one gallon to get home. But after people have heard the same sob story for a long enough time, somebody has to invent a new one which will inevitably be copied by others.
Assuming both the young man and the elderly gentleman are con men, they have probably both waited until dark to ply their trade. Dusk is the ideal time. If they waited too long there would be fewer pedestrians on the streets, and people would be harder to approach in the dark of night. They themselves would become more conspicuous to the policemen because there would be fewer people around them. On the other hand, if they started operating in broad daylight they would stand a much better chance of getting arrested.
It was important for Saki to establish that it was dark--but not too dark. That was why he described the atmosphere of dusk and even gave his story the title "Dusk."