The Smith family's much-needed vacation to the remote Swedish island of Svalta takes a dark turn when they arrive during preparations for a mysterious local festival that celebrates a dark history.

Unsettled by the unfriendly locals and strange rituals, they try to make the best of their trip, stubbornly enjoying the island's isolation and natural beauty. However, as the festival looms closer, the family realizes something far more sinister is unfolding--especially when they discover that a serial killer is on the loose.