Hee-yeon moves to her hometown near Mt. Jang, wishing her mother-in-law remembers how she lost Hee-yeon’s longing son, Jun-suh. One day, near a cave at Mt. Jang, Hee-yeon meets a girl in tatter and reminds of Jun-suh. Feeling sympathy, Hee-yeon decides to spare a bed until she finds the girl’s parents. Gradually, the girl mimics Hee-yeon’s daughter, Jun-hee’s name, voice, and look; eventually, calling Hee-yeon, mom. As the girl enters the house, strange things begin to happen to a family and at last, the mother-in-law who suffered from auditory hallucination disappears to the cave with the legend about a mysterious creature. Will Hee-yeon find her son? Will this family find happiness again?