In a distant realm, Eila has always taken care of her little sister, Carys, in their isolated, industrial mountain city. But when they and a stranger are hurled downriver into the vast unknown, they discover the environmental destruction that their city has wrought for the dangerous and beautiful creatures downstream. The three girls journey through fantastic lands to discover the truth about their existence that is more surprising than they could have imagined. Along with their new allies, they vow to return home to make things right...