For generations, the Folken have lived in total isolation. A self-contained society, they worship Bluegrass music and the legendary banjo picking of Jesus. For the Folken, the outside world inspires fear, not curiosity. Sarah Throckmartin is a typical 12-year old, living a typical Folken life - until her runaway dog, an old grudge, and a false prophecy combine to exile her and her brother Eddie from the Folken and everything they know. Together, Sarah and Eddie travel out into the wider world, discovering new genres of music at every turn. Making friends and enemies along the way, brother and sister find themselves drawn into a dangerous quest to find music's source - a mystical city known as... Agharta.