Murray, Mina, Connor, and Shen accidentally find a strange ship stranded nearby their town. The ship is surprisingly similar to a drakkar—an ancient Viking vessel—but with a torn sail and a name written in Greek letters: “Metis.” On board, the kids find traces of mysterious incidents, a strange cube covered in numbers, and a notebook with words on its cover: “Ulyss Mur, notes for the thirteenth book”… The four friends decide to set sail, and the ship will take them to a place their imagination and fantasies have never dragged them before.