yellow wallpaper

How does this quote give you a hint as to her mental illness? The narrator is excited about getting to see this mansion and beautiful garden: “The most beautiful place! It is quite alone, standing well back from the road, quite three miles from the village. It makes me think of English places that you read about, for there are hedges and walls and gates that lock, and lots of separate little houses for the gardeners and people. There is a DELICIOUS garden! I never saw such a garden.