A staircase leading to the dormitory of a remote boarding school usually has 28 stairs, but every so often there appears to be 29. When someone steps on the mysterious extra stair, the horror begins.

Once taken her job because of her appearance, a confident and enthusiastic woman, Hyo-jung visits a mysterious yoga institute run by an ex-actress where her radically changed friend told her to go. At the intensive training course, a young yoga master, nani explains to Hyo-jung and four other girls that only one person who masters the course most successfully can get the secret of ultimate and immortal beauty. there are five rules for them to follow during the one week course: 1. do not eat, 2. do not take showers within an hour after the class, 3. do not look at the mirror, 4. do not go out of the building, 5. do not call anyone. As the training goes on, girls get tempted to break the rules caused by hidden craving of each girl’s and Hyo-jung starts to sense there is something about this institute and an actress who doesn’t get old...