Saki seems to be deliberately leaving the ending of "Dusk" with an open question. Apparently the young stranger was a fledgling con artist who got a sovereign and a cake of soap from Gortsby by the sheerest coincidence. The elderly gentleman who had been sitting by Gortsby earlier was apparently an honest citizen who had accidentally dropped a cake of soap near the bench. When Gortsby returns to the area after giving the young stranger the sovereign and soap, he suddenly realizes that he has been swindled. His conversation with the elderly gentleman teaches him a lot in a very short time:

As Gortsby retraced his steps past the seat where the little drama had taken place he saw an elderly gentleman poking and peering beneath it and on all sides of it, and recognised his earlier fellow occupant.

"Have you lost anything, sir?" he asked.

"Yes, sir, a cake of soap."

Now the unanswered question at the end of "Dusk" is: What should Gortsby do? He knows what happened to the soap. He found it and was morally responsible for returning it to its rightful owner. Instead he gave it away to a trickster. Should Gortsby tell the elderly gentleman he found it? If so, should he offer to reimburse him for the cost of the soap? The rightful owner would expect him to, and might insist. That would mean that Gortsby would not only be out the sovereign he gave the young grifter, but he would lose several additional shillings paying for the soap. 

On the bench by his side sat an elderly gentleman with a drooping air of defiance that was probably the remaining vestige of self-respect in an individual who had ceased to defy successfully anybody or anything. His clothes could scarcely be called shabby, at least they passed muster in the half-light, but one's imagination could not have pictured the wearer embarking on the purchase of a half-crown box of chocolates or laying out ninepence on a carnation buttonhole. He belonged unmistakably to that forlorn orchestra to whose piping no one dances; he was one of the world's lamenters who induce no responsive weeping.

(Note that Saki describes him in a semi-humorous fashion. Saki obviously does not feel sorry for the "defeated." The Wikipedia article on Saki (H. H. Munro) states that he was a Tory and something of a reactionary.)

The loss of the cake of soap is obviously a misfortune for this old man. But he is a total stranger. What would Gortsby do? What would you do? Would you explain the truth and give the poor man enough to buy another cake of soap? I believe Saki is suggesting that Gortsby has already had enough of playing the Good Samaritan and that he would keep going on his way, saying, "I hope you find it." In that case he would end up with a guilty conscience as well as the memory of being swindled by the other stranger, and he might resolve never to get involved with strangers and their problems again. Gortsby might try to ease his conscience by telling himself that this elderly gentleman could be just another con artist who would tell him, if he got the chance, that he went out to buy a cake of soap and couldn't find his hotel. But even if he was a grifter, it was still his cake of soap that Gortsby gave away.

The story "Dusk" by H.H. Munro (known as Saki) tells us about a man named Norman Gortsby, who wanders around the city at dusk to take a look at the people who come out at this time of day. Gortsby claims that only those who need to hide from society, those who are miserable, and those who are in trouble are the ones who would go out during dusk.

While he is at the park sitting, he spots an elderly man who sits next to him. Instantly, Gortsby concocts a profile about this man based solely on his looks. The impression that the elderly man causes in him makes Gorstby believe that the man must be a loner, an angry man, and someone who is ignored. This, he bases on the fact that the elderly man is not showy, nor dressed to impress.

The story describes the elderly man in the following manner:

an elderly gentleman with a drooping air of defiance that was probably the remaining vestige of self-respect in an individual who had ceased to defy successfully anybody or anything. His clothes could scarcely be called shabby, at least they passed muster in the half-light, but one's imagination could not have pictured the wearer embarking on the purchase of a half-crown box of chocolates or laying out ninepence on a carnation buttonhole. He belonged unmistakably to that forlorn orchestra to whose piping no one dances; he was one of the world's lamenters who induce no responsive weeping.

What we actually see is the figure of a simple man. He is not flashy, petulant, nor asks for anything. He is the typical social figure that seems to dissappear in the crowds precisely because of its simple and transparent nature. However, to Normal Gorstby, these characteristics are symbols of a weakness of character. As a result, he feels repulsed by the man.

Contrastingly, when the flashy youth shows up and tells him the lies that he invents (to get money from Gortsby), Gortsby immediately feels a tendency to believe him and even identifies himself with the youth. When the young man tells him that he needs money because he has lost the address to his hotel, AND a bar of soap from the chemist shop, Gortsby does not believe him. However, when a bar of soap happens to show up underneath the sit where the youth was sitting, Gorstby resolved to loan him money and send him on his way.

In the end, we know that the elderly man is the actual owner of the bar of soap, that he is probably the one who lost it, that the youth may have even stolen it from him, and that Gorstby has been duped. This is the lesson to be learned: Age, demeanor and appearance do not dictate morals nor character. One cannot judge a book by its cover.