As the city prepares to celebrate Halloween with a grand costume party, Alice, a young student, discovers a strange stone of unknown origin. Following an accidental mishandling, she finds that the object has transformed the inhabitants into their respective costumes, while simultaneously bringing out their true natures. As unprecedented chaos engulfs the city, Alice and others decide to band together to survive this nightmarish night. They will have until the first light of dawn to find a solution before it's too late...