Dani, an American psychology student, is in a terrible relationship with her slacker boyfriend Christian. After she experiences a heartbreaking loss, Christian, who had secretly planned to break up with her, tries to make the relationship work and invites her to join him on a trip to Sweden. He and his friends, Josh and Mark, had originally planned to visit a small, rural village commune, the home of exchange student Pelle, in time for a nine-day, midsummer festival that the villagers hold every 90 years. What Dani, Christian, Josh and Mark fail to realize is that the villagers are part of a pagan cult. After they're given a drug designed to open them up to influence and break down their defenses, they soon discover horrifying secrets about the villagers and their festival.