In a world devastated by war that led to deadly air pollution, the few survivors have built a new life among the treetops, 200 feet above the ground. Ren, a resident of this tribe, faces a crisis as conditions worsen and breathing becomes increasingly difficult. She has always been haunted by the fear that nothing will change, and they will be trapped in the trees forever. When something finally shifts, it's not the hopeful transformation Ren had dreamed of. What will she do?