What is ironic about the title "The Open Window"?
The open window looks perfectly innocent. The fact that it is standing open suggests this is a perfectly safe environment. In this peaceful country setting, the inhabitants can leave their windows open and probably don't even bother to lock their doors. Yet the precocious and mischievous Vera can weave a story around the open window that will make it seem ominous and sinister. According to the girl, it was through that window that three men went to their deaths three years ago.
Out through that window, three years ago to a day, her husband and her two young brothers went off for their day's shooting. They never came back. In crossing the moor to their favourite snipe-shooting ground they were all three engulfed in a treacherous piece of bog.
The tragedy, Vera tells Nuttel, caused her poor aunt to have a mental breakdown. Her aunt now sits and waits for those male relatives to return for tea every evening. Framton Nuttel, the nervous visitor, believes the aunt must be really insane if she has been expecting her husband and two younger brothers to return for three years and still hasn't given up waiting. The fact that the window stands open seems pointless to Nuttel. The dead men can never return to life. Suddenly, everything changes. Aunt Sappleton cries out:
"Here they are at last!" she cried. "Just in time for tea, and don't they look as if they were muddy up to the eyes!"
Nuttel still doesn't feel threatened by the open window. He turns to look at Vera to show his sympathy, but the girl is staring at the window with a faked expression of horror. This makes Nuttel turn quickly to look where she is looking.
In the deepening twilight three figures were walking across the lawn towards the window, they all carried guns under their arms, and one of them was additionally burdened with a white coat hung over his shoulders. A tired brown spaniel kept close at their heels.
These can only be dead men who have finally struggled out of the bog and are returning home all covered with mud and dead leaves. The open window has become a menacing thing. It is too late to try to prevent the entrance of the living dead! Nuttel flees for his life. The reader then learns the three men have only been gone for one day. It was all a practical joke. It is of course ironic that Nuttel is staying in the area for a "nerve cure." His London doctors have ordered:
"Complete rest, an absence of mental excitement, and avoidance of anything in the nature of violent physical exercise."
The title "The Open Window" is intentionally deceptive. The tall window symbolizes the peacefulness and security of English country life.