When things fall down, who lifts them up? 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. When Gran's friend, the difficult-to-impress Catalina Catalan, presses a silver handle into a hillside and opens a doorway to underground, he knows that she is extraordinary and brave, and that he will have no choice but to follow her, and help her save the town (and the known world). With luck on their side, and some discarded hockey sticks for good measure, they might just emerge as heroes.