In a small, coastal California town, as they prepare to commemorate the centennial of their founding, strange occurrences begin to unsettle the community. At the stroke of midnight, a mysterious, glowing fog envelops the town, bringing with it an eerie sense of dread. The local radio DJ, who broadcasts from a lighthouse overlooking the sea, picks up on the phenomenon and keeps the listeners updated on its movements. Meanwhile, the town's priest discovers an old journal that reveals a dark secret about the town's origins, hinting at the true nature of the approaching fog.

Simultaneously, a group of fishermen out at sea are engulfed by the fog, experiencing its malevolent presence firsthand. Back on land, a young hitchhiker arrives in town and quickly discovers that the normally idyllic location is being pervaded by a chilling mist. As the fog rolls over the town, cutting off communication and leaving the residents isolated, they soon realize that it carries vengeful spirits. These entities are seeking retribution for wrongdoings committed a century ago, and as the townsfolk strive to survive the night, they must uncover the historical sins of their ancestors in hopes of appeasing the phantoms hidden within the fog.