The Most (Un) Boring School in the World: The Secret Class Room (vol. 2)

After the turbulent field trip in volume 1, the obscure Inspector reappears at Max's and Frieda's school and has a mission for Max: He is to lead the class to the "secret classroom" - given that the school building used to be a prison. Together with Frieda and his class, Max bravely takes up the creepy trail through the school's winding corridors until he comes across a well-hidden secret passage and a file from an escaped prisoner turns up...