"The Open Window" by Saki cleverly addresses the theme of deception. The niece, Vera, convincingly tells the story of her aunt's "great tragedy" after enquiring that the visitor, Mr. Framton Nuttel, knew "practically nothing" about her aunt. He only possessed a letter of introduction given to him by his sister who hoped he might meet some nice people in the area. Vera then realizes that Mr. Nuttel would be a perfect victim for a little "romance at short notice," and she creates an elaborate story about her aunt's "great tragedy."
Mr. Nuttel has absolutely no reason to distrust the niece and completely believes every detail of her made-up story. The reader, also like Mr. Nuttel, finds themselves buying into Vera's romantic fabrication as well. Her story is convincing and grounded in the reality of the open French window in the room, which adds a sense of concrete believability to Vera's deception.
Only at the end of the tale when Saki reveals the girls' predilection for "romance at short notice" does the reader gain an appreciation for the fact that she has been duped along with Mr. Nuttel. Saki's creation of the mischievous niece and her penchant for wild stories perfectly illustrates the theme of deception.