In Autumnal, the city of eternal Fall, Sienna—an apprentice witch, is tasked with lighting the sacred Jack O’Lantern, which keeps the balance between dreams and nightmares in their world, during the annual Halloween festival.

But when the pumpkin is stolen by a mysterious group of shadows, Sienna has no choice but to dive into the realm of Nightmares to recover it before the clock strikes twelve, and chaos erupts between the two sides of the Sleep World.

With the help of an unexpected someone, she will soon learn that the line between good and bad is blurrier and grayer than the cloudy personality of her companion.