A group of teenagers are trying to solve a mystery of a puzzle created and left to them by the dead boy.

The time is 1945-46. 10 year old Eda and his friend Tonda live in a small village outside Prague. In school, their class is so wild and indisciplined that their teacher quits and is replaced by the militant Igor Hnidzo. He is very strict – but also very fair. His weakness though, is his interest in young women.