Lee Sona is the granddaughter of a hereditary haenyeo—women divers. After an unsuccessful attempt to conquer the capital, she returns to Jeju Island to her grandmother to start life over. Sona suffers from a panic fear of depth—bathophobia. She despises the profession of diving and can’t seem to get along with her grandmother. After returning to her hometown, unexplained frightening things begin to happen to her, leading her to uncover one of the most terrible secrets in her family.