How does the author use foreshadowing in Why I Live at the P.O.?

Sister's comment, "It's usually so quiet here," adds a new twist to the humor in the story. The sentence is comic because its speaker does not realize that we have to take it as an absurdity; we have heard nothing but noise since the story began. This comment also has a sinister edge to it, for the longing for separation and silence that it reveals foreshadows the dark edge to the ending of the story, when "quiet" at great cost is finally achieved.