Every year, one of the Dutch islands celebrates the mysterious, age-old festival of 'Sunderum'. Non-islanders are forced to leave, prying eyes are not wanted on the island. Daan and Judith are a couple from Amsterdam who have been in a happy relationship for seven years. To celebrate this anniversary, they accidentally end up on the island, this very weekend. When the young city-dwellers refuse to leave, it soon becomes clear that they will not only have to face the angry islanders. As tension increases, they will be forced to face demons of their own.