On Halloween night, a mysterious dog with glowing eyes appears at Lucy's doorstep. Following the strange hound into the forest, Lucy discovers an ancient magic intertwined with her own fate. The dog, Fangroot, is a cursed guardian, tasked with protecting the hearts of magical realms that connect her world to others. As dark forces rise, seeking to unravel these realms, Lucy and Fangroot must race to find and protect the hearts before it's too late. Their journey takes them through enchanted forests, forgotten realms, and hidden worlds in a race against time to save the balance of magic.