Ally Clement is throwing an intimate Halloween party for her closest friends. But before the festivities can really begin, a stranger drops by with a Halloween treat of her own. The mysterious gift turns out to be an ancient curse sealed in a bottle and when it's released, it transforms Ally into the most hideous "mean girl" anyone has ever encountered. Now, Ally's two best friends, Ramona and Lilith, must find a way to exorcise their cursed friend... before her mom gets home.