It's 1969 at a strict English girls' school where charismatic Abbie and intense and troubled Lydia are best friends. After a tragedy occurs at the school, a mysterious fainting epidemic breaks out threatening the stability of all involved.
Marcella Backland left the Metropolitan Police for the sake of her family, only to have her husband leave her. She returns to her job on the murder squad, investigating a case that seems disturbingly familiar to her.
Following the events at home, the Abbott family now face the terrors of the outside world. Forced to venture into the unknown, they realize the creatures that hunt by sound are not the only threats lurking beyond the sand path.