A summary of "The Open Window" doesn't present a chronological straight time line because there are many flashbacks. Flashbacks take the reader back to a time before the opening moments of the story and give vital information that relates to the narrative's present tense events. For example, the story opens in the present with the "self-possessed young lady of fifteen" apologizing for her aunt's delay and proposing that Mr. Framton Nuttel will have to settle for being entertained by the young lady. The first flashbacks follows in which we are told that (1) he has a nervous condition and is undergoing a doctor's "cure; (2) that his sister intervened with letters of introduction; (3) that Framton is given to being a moping recluse. We are neatly brought back to the present by Framton wondering if the aunt he was waiting to see was one of the people his sister had said were nice.
In the present, the niece ascertains that Framton has never been in the district before, that he knows no one in the area yet, and that he knows nothing of the young lady's aunt he is there to visit. Now she hatches her wicked plan and, after alluding to the open ceiling-to-floor French window and the month of the year, begins her tale about her aunt's "tragedy" that "happened just three years ago." In a flashback of her own devising and that forms the critical part of her tale, she tells how husband and brothers were lost in a bog while on a daily hunting trip. Then, returning to the present, she speaks of how her aunt still believes they will return from the dead to walk in through the open window as they were accustomed to doing.
The aunt now enters and begins normal conversation with normal reference to husband and sons being due to walk in through the open window at any moment. Framton interrupts her cheery talk by exclaiming that he is to have complete mental rest. Just then, the aunt, Mrs. Sappleton cries out, "Here they are at last!" In a fit of horror deepened by the girl's good dramatic acting, Framton flees the house as the three men enter through the open window. The resolution reveals the girl keeps her secret evil to herself while the aunt classifies Framton as some inexplicable and "most extraordinary man."
"I expect it was the spaniel," said the niece calmly; "he told me he had a horror of dogs. He was once hunted into a cemetery somewhere on the banks of the Ganges by a pack of pariah dogs, and had to spend the night in a newly dug grave ...."