Several friends travel to Sweden to study as anthropologists a summer festival that is held every ninety years in the remote hometown of one of them. What begins as a dream vacation in a place where the sun never sets, gradually turns into a dark nightmare as the mysterious inhabitants invite them to participate in their disturbing festive activities.

Following the death of the Leigh family matriarch, Annie and her children uncover disturbing secrets about their heritage. Their daily lives are not only impacted, but they also become entangled in a chilling fate from which they cannot escape, driving them to the brink of madness.