Destiny? Or doom? An ancient prophecy calls for a drummer to take up his sticks on the summer solstice and pound out a beat that might save the world from an army of trolls, ogres, and other nightmare creatures. Sixteen-year-old Noah Keene knows nothing of his destiny when he runs away from his home on the Oregon Coast. He knows only that he's sick of school, chores, and his father's rules. His thirteen-year-old sister, a brainy budding scientist, follows Noah to Humbug Mountain where they're captured by creatures she calls grungoids. Deep in the mountain's caverns, Abby learns she also has a destiny-to tap the power of trust and find a way to command the Darksuckers.