The Yellow Wallpaper by Charlotte Perkins Gilman

The Yellow Wallpaper tells the story, through diary entries, of a woman confined to her room by her physician husband John for a mysterious illness diagnosed as "nervous depression." John, following the rest cure treatment popular at the time, forbids her from writing or any mental stimulation.

Left to her own devices, the unnamed narrator becomes fixated on the hideous yellow wallpaper in her room. Her obsession grows as she becomes convinced there is a woman trapped behind the patterned design. As her mental state deteriorates, the lines between reality and delusion blur. She secretly peels back the wallpaper, becoming increasingly consumed by the idea of freeing the trapped woman. By the story's end, the narrator has fully descended into madness, believing she herself is the woman and creeping around the room at night.