How is suspense built around "The Open Window"?
The open window as the frame for her fabricated story lends a false sense of truth as openness is usually suggestive of veracity. By this initial deception, Vera establishes suspension of disbelief on the part of Mr. Nuttel. Her use of words such as tragedy in a "restful country spot [where]tragedies seemed out of place" creates immediate suspense. Then, Vera points to the window and suggests its connection to the "tragedy." Her breaking voice that becomes "falteringly human" as she says that the bodies were never recovered certainly adds to the suspense, as well.
Certainly, there is also some suspense when, after Vera has told Mr. Nuttel that the aunt refuses to believe that the men of her family are gone, and the aunt appears, Nuttel wonders what this woman will say about the open window before them.
After Vera ascertains that Mr. Nuttel knows nothing about her family, she makes the open window the center of the conversation. The fact that the hunters are lost out on the moors add mystery to the story. At first, the open window symbolizes the grief felt by Vera's aunt at the loss of her husband and sons. When her aunt comes into the room, she again brings attention to the open window, waiting for her husband and sons to return. Vera's aunt seems to authenticate Vera's story, and this adds more suspense to the story, especially when we hear the father and sons returning from their hunt.