The tone of "The Open Window" is witty and derisive, which emphasizes its satirical nature. Although there is an element of contempt found in this tone, it is mixed with pity; Saki shows some degree of sympathy in his ridicule of Mr. Nuttel and the situation that unfolds.
Just as the mood shifts when Vera briefly takes over the narration and tells the tragic story about the men who were engulfed by the bog, the tone becomes markedly somber—on the verge of melodramatic—during this part. Nevertheless, the tone remains mocking throughout most of the story. The third person narrator's vexed yet amused attitude towards Mr. Nuttel corresponds with Saki's attitude to the customs and people he is satirizing. An example of this is the narrator's commentary on Mr. Nuttel's explanation of his physical health:
[...] announced Framton, who laboured under the tolerably wide-spread delusion that total strangers and chance acquaintances are hungry for the least details of one's ailments, their cause and their cure.
The third-person narrator, who mostly refrains from expressing an opinion on the characters and events of the story, can't help but express how hopeless Mr. Nuttel is during this part. The forceful diction is decisive for shaping the narrator's tone at this point. Instead of saying something along the lines of "Mr. Nuttel thought that Mrs. Sappleton and Vera might want to know why he's in the countryside," the narrator characterizes Mr. Nuttel's narcissistic hypochondria as a delusion that he labors under. At the same time, the narrator underlines that this phenomenon is "tolerably wide-spread." While the hypochondriac obsessions of Mr. Nuttel are without a doubt delusional, he is far from alone in thinking like this—hence, Saki's reason for featuring it in his satire. The story's tone makes it feel like readers are supposed to roll their eyes, but perhaps with a smile of pity.
