Annoyed by her big brother and her own bad temper, Yuki throws her house keys down a manhole. When she goes after them, she arrives in a strange underground world, ruled by the mighty Mud Princess. In a place where lost things are found and anger tastes delicious, Yuki finds new friends and learns that she's not the only person living with difficult feelings... Join beloved picture-book creator Beatrice Alemagna on a messy, magical adventure of self-discovery!