Invisible Lake (#2). Sheller A.

What a class director at the Fjell and Emil school! In his lessons, the guys play and joke all the time! Only now many parents do not like this: they believe that Mr. Unterberg has no place in elementary school. Therefore, the director is very upset and does not leave home at all. But Fjell is sure: in fact, Mr. Unterberg fell ill with a mysterious disease! And you can cure it in only one way: to bring water from a distant lake, the road to which no one knows. Will Fjell and Emil be able to help the school principal?