Summer holidays are over and it's time for a reunion between the boys from Shiverstone Castle and the girls from the Rosenfels School. Their rivalry continues when they face off at the annual competition held at Lake Kapell. Yet their antics are cut short when Count Shiverstone's blimp crashes. With the Count recovering, the school suddenly is at the brink of financial ruin. His cousin Kuno comes up with a solution; selling to a Chinese investor who wants to move the estate to China where it is supposed to become a medieval theme park. When the boys realize what is about to happen, they hear of a long-forgotten treasure. Maybe this way they can save the castle – but is this treasure just a myth or is it real? This time, the kids have to stand together to save their beloved Castle.