What is the summary of "Dusk" by Saki?I am not sure where to begin.

"Dusk" is another one of Saki's darkly ironic tales.  The protagonist, Gortsby, spends the duration of the story observing people scurrying about at dusk.  He thinks of most of the people whom he watches as being defeated and believes that dusk represents the time of defeat for humans.  The story features third person limited point of view, so most of the characterization of Gortsby occurs through Saki's writing down Gortsby's thoughts.  The character possesses a cynical view of the human state and has experienced some type of defeat of his own--Saki never details what that failure is on Gortsby's part; he simply writes that it is not a financial failure.

The first passerby whom Gortsby observes is an older man who seems dejected and reluctant to go home.  The protagonist thinks that he most likely receives no respect at home or that he goes home to a place that he can barely afford to keep. Shortly after Gortsby's observation begins, the old man gets up from the bench and walks away.

The second "victim" of Gortsby's cynicism is a young man who is better dressed than the first and who makes a show of being very upset.  Gortsby initiates a conversation, and the young man tells him that he has forgotten the name of the hotel at which he is supposed to be staying and that he has no money on him.  He left his hotel room to get a bar of soap and a drink and cannot find his way back to his lodgings. Gortsby is skeptical about the young man's integrity and mentions that he has a good story but that he failed to produce proof of his predicament--a bar of soap. The young man realizes that his con has failed and flees the scene.

Gortsby prepares to sit back and gloat over his wise judgment of human nature when he spots a wrapped bar of soap near the park bench.  He thinks that he has misjudged the young man, runs after him, apologizes for disbelieving him, and gives him money.  Gortsby walks back to his bench, slightly chagrined.  Moments later, the first old man returns to the bench and tells Gortsby that he is looking for his bar of soap.

Saki ironically leaves the reader with the lesson that one should not be too confident in his or her view of the human character.