In one royal forest, where coal miner Patočka lives and works, the friendly dragon Mrak settles down. The king's lackeys come across him while hunting and, terrified, go to sell the news to the king. He is currently organizing his daughter Viola's birthday party. The hunters describe the dragon in terrifying colors, and so the king concludes that the dragon will, according to tradition, want the king's daughter. So he announces a reward for killing the dragon, but no one wants to fight him. The only one who applies is the princess's favorite, the lutenist Marian, but the king does not like him, so he throws him out. Her brother Jan wants to save the princess, but the king doesn't want to allow it...

Inseparable friends Štěpán and Kendy are students in their final year of high school. When they are in the principal's office after the trouble with the rather scandalous song "On the Carpet", the school principal gives them the idea of ​​rehearsing a theater performance. They decide on Tyl's Forest Maiden in a rather unconventional version - with music, singing, and several unusual props. While Kendy sees the theater as not only an opportunity to enjoy himself, for Štěpán it is a chance to get closer to the charming Marcela Borůvková. What was originally just a student recession soon starts to get out of hand for both authors, not only because of the quirky cast but also because of information in the press, which is taken care of by the father of one of the classmates. The business is gaining in size, and even a television station is contacted, which shows an interest in making a program about the performance. At that moment, the disaster seems inevitable to Štěpán and Kendy.