Sera Lighthaven has always felt as if she didn't quite belong among her people, the Cerulean, who live in the City Above the Sky. She is curious about everything--especially the planet that her City is magically tethered to--and can't stop questioning things. Sera has always longed for the day when the tether will finally break and the Cerulean can move to a new planet. But when Sera is chosen as the sacrifice to break the tether, she feels betrayed...