Ten years ago a deadly and mysterious infection spread across the Earth's terrain, forcing humankind to live in communities precipitously built above the ground. Growing up on Needle Three, Jo barely remembers a time before darkness enveloped the world. But when our hero's community comes under attack by the despotic Charon and his forces, Jo and his friends must decide whether or not to venture across the wasteland in search of a safe haven as the world hangs by a thread.