The young man who tells about losing his hotel room in Saki's "Dusk" is trying to cheat Gortsby out of some money. The elderly gentleman who sells the narrator's mother an umbrella is not cheating her because she is getting a twenty-pound silk umbrella for only one pound. This elderly gentleman is, however, more of a criminal than the young con artist in "Dusk" because he is stealing umbrellas and selling them.
The young man's story is ingenious. The umbrella man's story is not. He may look like a gentleman, but he is a common thief and a drunkard. He must be a drunkard if he can drink three ounces of whiskey straight down and then go out to raise more money with another stolen umbrella to buy himself another triple-whiskey. It does not seem that it should take much cleverness to sell a silk umbrella worth twenty pounds for one pound, especially to someone caught in the rain without any protection.
Roald Dahl bolstered his story by having it narrated in a straightforward manner by the young daughter of the woman who buys the umbrella. The precocious girl adds humor to the tale with her comments about her mother. For example:
My mother's chin was up and she was staring down at him along the full length of her nose. It is a fearsome thing, this frosty-nosed stare of my mother's. Most people go to pieces completely when she gives it to them.
There is only minor conflict between the elderly gentleman and the woman who finally buys the umbrella. The major conflict is between the mother and daughter. The girl wants her mother to be more open and trusting, while the mother is trying to teach her daughter to be more skeptical and cautious.
There is no third-party narrator in Saki's "Dusk." The story is told by an omniscent narrator through Gortsby's point of view. He does not end up with anything in exchange for the pound he gives the young man because he is tricked into believing he is only making a loan and will get his money back in the mail. Obviously, Saki's story was much harder to plot and much harder to make convincing.
One of the problems with the plot of "The Umbrella Man" is that the mother and daughter have to follow the elderly gentleman for many blocks and spy on him through the window of The Red Lion in order for the reader to understand the denoument. The girl says:
He was scuttling along like a rabbit and we had to walk fast to keep up with him. The rain was pelting down harder than ever now and I could see it dripping from the brim of his hat onto his shoulders.
Would the mother really want to follow the elderly gentleman just out of curiosity--and especially in such weather? We end up feeling sorry for the elderly gentleman because he is old, because he is obviously poor, and because he is an alcoholic. He won't live very long running around in rainstorms selling stolen umbrellas.