A lonely, neglected orphan named Lily writes a Christmas letter pleading for a puppy. Unable to spell "Santa," she accidentally addresses it to Satan—and the letter, decorated with a crooked pink heart, lands directly on the throne of Hell itself. Amused and insulted, the ruthless Demon King decides to deliver a monstrous Hell Nightmare as a cruel joke. But instead of terror, Lily hugs the beast and names it Fluffy. Trapped by a magical contract and the child's unwavering belief that he is her "courier," Satan is forced into babysitting, plumbing repairs, and parent-teacher conferences. When Archangel Gabriel descends to purify everything tainted by darkness, the Lord of Hell must decide whether to walk away—or burn Heaven itself to protect his new family.
