After a family tragedy, a young American couple joins some friends at a midsummer festival in a remote Swedish village. But, what begins as a carefree summer holiday takes a sinister turn when the insular villagers invite their guests to partake in festivities that grow increasingly unnerving and viscerally disturbing.

When the matriarch of the Graham family passes away, her daughter's family begins to unravel cryptic and increasingly terrifying secrets about their ancestry.