"The Open Window" features several instances in which the story's comic edge comes from the reader knowing more than some of the characters do. Initially, Vera tricks not only Mr. Nuttel but also the reader with her story about the three men who did not survive their fateful hunting trip three years ago. Eventually, however, the reader realizes that Vera has successfully tricked Mr. Nuttel. At whatever point the reader catches onto this, the rest of the story is extra funny because the reader, having been duped, now shifts from Mr. Nuttel's vantage point to Vera's.
Mr. Nuttel, who is after all present for all of the story's early events, is not the only character that falls prey to dramatic irony. The reader's understanding of the situation definitely exceeds that of Mrs. Sappleton; given that she is absent when Vera tells the story, she is completely in the dark about the key context Mr. Nuttel has about her when she appears in the room. This is why she is astonished when Mr. Nuttel darts off for no apparent reason, before they have a proper conversation and before he gets the chance to meet her husband and brothers.
"'A most extraordinary man, a Mr. Nuttel,' said Mrs. Sappleton, 'could only talk about his illnesses, and dashed off without a word of good-bye or apology when you arrived. One would think he had seen a ghost.'"
The last remark is ironic because only Vera and the reader know that Mr. Nuttel actually did think he had seen a ghost—or rather three. Saki had already had fun with this morbidity earlier in the story: upon seeing the men return from their hunting trip, Mrs. Sappleton essentially tells Mr. Nuttel and Vera that it looks as though the men had been buried alive.
'Here they are at last!' she cried. 'Just in time for tea, and don't they look as if they were muddy up to the eyes!'
Little does Mrs. Sappleton know that this corroborates Vera's claim that the men were engulfed by the bog. It is this exact incongruity between the knowledge of the characters and the knowledge of the reader that makes Mr. Nuttel's reaction to the return of the men and Mrs. Sappleton's reaction to Mr. Nuttel so funny.
Before the story ends, Saki cannot help but play with the characters' and reader's incompatible understandings of the situation. When Vera rationalizes Mr. Nuttel's flight as being prompted by his deep-seated fear of dogs, which she again narrates a story to explain, the audience's relative awareness of what is going on (compared to that of Mrs. Sappleton and the men) further increases. While the reader did not immediately detect the deceptive quality to the story she told Mr. Nuttel about Mrs. Sappleton, it is now obvious to the reader that Vera is a cunning liar who has managed to dupe both a stranger and her aunt. Not only did she shape Mr. Nuttel's knowledge of Mrs. Sappleton, she also shapes the Sappletons' knowledge of Mr. Nuttel. The punch of the story is largely shaped by this dramatic irony, as the reader has slowly gone from gullible receiver of Vera's tall tales to someone on the inside.
