Master Wu, Misako, and Kevin Kiesel are on their way to an unknown island. When the Ninjas no longer hear from the three, they set out to search for them. On the island, the Ninjas are captured but manage to escape and return to Ninjago with Wu, Misako, and Kevin Kiesel. Upon their arrival, Nya realizes that her powers are no longer working, while an unusual force is developing in the depths of the sea. To help, Nya's and Kai's mother arrives, and together they venture into the depths of the ocean. What awaits our heroes there?.