Kairo discovers a hidden staircase beneath the desert that leads to the lost underground city of Lumeris, where an ancient lighthouse suddenly reactivates after a thousand years of silence. With the help of a mysterious Guardian, he learns the lighthouse was once a beacon that guided visitors from the stars but also attracted dangerous invaders. Realizing the signal has been detected again, Kairo destroys the lighthouse to protect his village, allowing the ancient city to return to its long sleep beneath the desert.
