Melanie is a new pupil at the Otto Leonhard High School, and Felix takes a real shine to this newbie, much to the annoyance of Ella and Felix’s gang. They believe that Melanie is responsible for a number of small thefts that have been happening at the school since she arrived.
Events take a drastic turn when the class goes on a school trip. When Felix’s friends almost mess up his date with Melanie, he shrinks them spontaneously to a tenth of their size. Just for a short time, he thinks to himself. But once Melanie has left, the magic ball to restoring his friends to their proper size has also disappeared. Is Melanie behind the thefts after all? In the process, Felix not only has to shrink himself, he also has to confess his love to Melanie and admit his mistakes to his friends. They have to find the real reason for this mysterious class trip and confront their vindictive opponent: the former head teacher Hulda Stingbeard, who has risen from the dead and is determined to banish the good school ghost Otto Leonhard from the school building once and for all.