Perched atop a mountain is the Blue Moon Inn, the long-standing residence of Matthew Hopkins, known to locals for generations. Legend has it that every hundred years, the moon takes on a blue hue, triggering a series of bizarre and frightening occurrences. As this rare event approaches, a curious trio—a scientist studying the stars, a practitioner of astrology, and a filmmaker documenting the phenomenon—gathers at the inn, oblivious to the horrors awaiting them. Each faces their own terrifying ordeal, leading to a startling climax.