The mood of "The Open Window" begins in a ordinary manner. It is merely an introduction from Framton Nuttel to Mrs. Sappleton. As the story progresses, the mood becomes suspenseful. As the niece tells her tall tale, the reader is as intrigued and is Framton Nuttel. When Mrs. Sappleton claims to see her husband and her brothers walking toward the house, the reader has sympathy for poor Mrs. Sappleton. Then when the neice and Framton see the same images, the reader is anxious, thinking that Mr. Sappleton and the other two men are ghosts, apparitions.
When Framton makes his quick exit, the reader begins to realize that the niece has told a tall tale. As the tone becomes humorous, the reader is relieved to know that the niece has told a terrific tale that frightend both Framton and the reader.
At the ending of the story, the reader is so relieved until he or she cannot become angry with the niece for her practical joke. The ironic ending leaves the reader filled with, first, apprehension and anxiety. Then the mood becomes one of humor and relief.