According to the narrator what is trapped behind the wallpaper

The Narrator believes that she can see a woman trying to get out from her yellow wallpaper in their bedroom. The narrator had been suffering from a serious case of nervous depression. She used to have a very creative imagination which led to her fixation on the patterns of their yellow wallpaper. As the day passed, she believes that there were gradual changes in the pattern. From the very start, she knew that it was not her imagining things but something is really queer about their new house. In the end, the narrator realized, she was the woman trying to get out from the yellow wallpaper pattern.