The story "The Yellow Wallpaper" is a tale about mental and physical oppression. This oppression comes as a result of a woman's personal struggle with what her peers call "nervous prostration", but what the modern reader can certainly categorize as post partum depression.
These poignant words are muttered by the narrator, who is also the main character:
I really have discovered something at last.
Through watching so much at night, when it changes so, I have finally found out.
The front pattern does move -- and no wonder! The woman behind shakes it!
Our main is taken into an isolated house where she is deprived of all the things that provide her with a mode of escapism: She cannot write, nor communicate openly. She is simply left to "rest" in a room under the assumption idea that, with the least amount of stimulation, the depression will somehow get better.
However, the opposite happens. The woman gets fixated on the yellow wallpaper that decorates the walls of the room and it is then when she begins to assume that there is a woman trapped inside of the wallpaper, much like she is, trapped into the current situation.
It is for this reason that she channels her ordeal through the yellow wallpaper and is determined to liberate the woman inside by tearing down the paper. This moment of psychosis, however, is allegorical to the chaos that she experiences inside her mind and soul.