Morfa Halen is a precariously situated Welsh town, nestled between high mountains and a rapidly encroaching sea, threatening its very existence. As a rare storm, which occurs once in a generation, begins to gather far out at sea, former detective turned teacher, Jackie Ellis, discovers the body of her 8-year-old student, Cefin, apparently drowned. The discovery sends shockwaves through the community, reviving the ghost of an unsolved case that shook the town three years ago - the disappearance of Jackie’s niece, Nessa, which cost her career.