Trapped in the rural town of Mayflower, Pennsylvania, Jessica and her daughter Suzy are caught in the midst of a growing nightmare—cell towers are down, the bridge has been destroyed, corpses are vanishing, and neighbors are turning into monsters. Taking refuge in a local church with the town sheriff and the remaining townsfolk, they uncover a terrifying truth: the town has been completely cut off, and a nuclear strike is imminent. With time running out and vampires battering the church doors, their only hope of survival lies in a long-forgotten Prohibition-era tunnel beneath their feet.