What if the ground beneath your feet was not made of solid earth and stone but had been hollowed into hundreds of tunnels and passageways? What if there were mysterious forces in these tunnels, mere inches below you as you sit in class or eat a banana? What if it were up to just two kids to stop these forces? What would it feel like to know the fate of an entire town rested on your shoulders? Twelve-year-old Gran Flowerpetal is about to find out.