Two weeks after entering the magic school of Avalon, Merline discovers her Gift: she can communicate with the undines, those little aquatic creatures. What a joy! But her happiness is short-lived. Because, this time, it is already certain: Morgana has been freed from the prison where Merlin had locked her up. And the terrible evil witch is determined to take control of the school... by force, if necessary! Will Merline be able to save Avalon? Fortunately, the young apprentice can count on her faithful friends, Rose and Nina, and their respective Wizard Cats.