A surprise birthday party becomes a living nightmare for city-dwelling couple Sadie and Rick and their friend Jonny. They are invited to visit the remote tidal island of Amen by Corinne, an enigmatic local who hopefully holds answers to long-buried family secrets. Amen is historically populated by a close-knit community who discourage strangers from visiting. So why have these three outsiders been allowed onto the island? Their arrival brings horrific consequences as they find themselves trapped by the tide and at the mercy of the islanders. These visitors will wish they'd never been born.