Juf Roos is jarig: Hip hip hurray, it is Miss Roos' birthday! Of course she organizes a nice birthday party and everyone is invited. Miss Roos her funny neighbor, Gijs, adorns the colorful mill in which Miss Roos lives. But Gijs uses way too many balloons. Much to their horror, the mill takes off due to the many balloons. Miss Roos and Gijs are still in it! They have an exciting adventure around the world in their flying mill. Will they be back in time to treat in Miss Roos her class?