On the far side of the world, a secret song is waiting... The mers who are searching for the Treasures of Atlantis have braved the challenge of the deep. Only one more test lies ahead of them: to find the song that will lead them to the Labyrinth. In the stormy waters of home, their friends must take the ultimate risk to find out the Oldmers' plans. There is danger in the dark caverns, and danger on the reef, but the greatest threat of all is the mer who swims with them. Will they find their way to the Labyrinth, and make Hraun the Huntmaster the ruler of the sea? Thus continues the epic tale of Poseidon's Children, as they risk their lives in uncharted seas...