Lotte and Thijs go to a great school and have a sweet teacher, Miss Evi. But then the awful Miss Brakel becomes principal and makes all sorts of rules: no phones, birthdays are no longer allowed, and treats are strictly forbidden. So the class gives her a nickname: Miss Vomit. They devise a plan to get rid of her, while Lotte also has a secret that needs solving. Can Miss Evi's magic ring help?