The narrator in The Yellow Wallpaper is clearly suffering from some sort of mental illness. She is confined to a small room in an attempt to recover from her illness, but she is constantly watched by her husband and is not allowed to leave the room. The wallpaper in the room is yellow and the pattern is said to be “creeping”. This causes the narrator to become obsessed with it and start to believe that there is a woman trapped behind it. She starts to act like the woman behind the wallpaper in an attempt to free her, but this only causes her husband to watch her more closely than ever before.
It’s unclear what exactly happens at the end of this story, because we never find out how it ends for either character involved: The narrator or her husband (who may also be mentally unwell).