Much of the imagery and Saki's use of descriptive words add to the surprise one may find at the end of "The Open Window."
First, Saki's use of imagery shows the setting to be a place of peace. The house is one which suggested "masculine habitation." given that Framton Nuttel is male, it would seem that he should feel very at home in a place which speaks to the masculine nature.
Vera's description of the tragedy which struck her family can leave readers feeling rather subdued and sympathetic. As Mrs. Sappleton banters on about her husband and brothers returning, readers can feel even more sympathetic towards the story given one can infer that she (Mrs. Sappleton) may be a little "confused."
Essentially, the engaged reader may pick up on the hints that men do actually live there, but the fact that Framton is at the Sappleton's to rest leaves one not expecting the group to walk into the house.
Therefore, words and imagery which details the surprise ending for "The Open Window" can be constructed as follows.
The secluded and sobering setting of the Sappleton home offer no suggestion to the horror which Framton Nuttel is to experience. Instead, the fact that Framton is there to rest suggests a rather slow and passive story. Instead, curious readers, hoping for a horrific twist, do receive the ironic twist they desire. The open window does not offer the relaxing view one would hope for; instead, the window shows there to be more to Vera's story than a cautionary tale. One may have assumed that Framton actually sees headless, bloodied, mud-caked ghosts walking up to the house (given the way Framton ran in horror).