What effect is described in the above story? Why would such an extreme reaction help reader understand what is happening in the story.
The questions belong to this passage.
Framton grabbed wildly at his stick and hat, the hall door, the gravel drive, and the front gate were dimly noted stages in his headlong retreat. A cyclist coming along the road had to run into the hedge to avoid imminent collision.
The passage that you are referring to is the escape by Mr. Nuttel from the Sappleton home at lightening speed. He is running away from, what he thinks, are the ghosts of Mrs. Sappleton's husband and brothers who have just risen from the dead out of the bog.
It is amusing to think that Vera, has so altered Frampton Nuttel's perception of reality, that he believes her story so thoroughly, that he is terrified beyond his wits when he sees the three men approaching the open window. He thinks they are ghosts.
He not only gets up and runs for his life, he leaves behind a perception for Mrs. Sappleton that he is rude and a bit crazy. Running out of the Sappleton's home provides an opening for Vera to tell another tall tale, this time about how frightened Mr. Nuttel is of dogs.
Saki is telling the reader that perception is reality. He is telling the reader that, if an individual is convincing enough in her conveyance of a story or situation, that the story can shape or alter the perception of the listener, thereby creating a new version of reality. Such as in Frampton Nuttel's world, where ghosts rise from the swamp to return home on the anniversary of their deaths.
Saki's story "The Open Window" is about a fifteen year old girl Vera's prank on a totally unsuspecting stranger Framton Nuttel who had come to the English countryside for rest and relaxation. His sister had asked him to meet one Mrs.Sappleton a former acquaintance of hers and the story begins with his visit to Mrs.Sappleton's house. While he is waiting for Mrs.Sappleton's arrival, her fifteen year old niece Vera after confirming that he is a complete stranger to the neighbourhood spins a yarn about how exactly three years ago Mr.Sappleton and his two younger brothers were drowned in the bog when they went hunting. Vera tells Framton that Mrs. Sappleton always leaves the french window open on that particular day every year hoping that her husband and his brothers would return. Mrs. Sappleton arrives and she tells Framton that she is expecting her husband and his brothers to return soon from their hunting trip. On hearing this Framton becomes nervous and as soon as the hunters are seen outside in the lawn crossing the french window into the room Framton absolutely terrified imagining that he has seen the ghosts of Mrs.Sappleton's husband and her brothers rushes out of the main door of the house and into the open.
The effect is one of comic irony. It is based on man's unreasonable fear of ghosts. The humour results from the spirited inventiveness of Vera which has made Framton more nervous than he was at the beginning.