Karlík is likely to fail his Czech exam. His teacher therefore gives him some homework which will decide the final mark. The theme of the style exercise is choosing the correct lighting for the home. Karlík's father borrows a specialist brochure on the subject from a friend. He learns a thing or two himself when he realises that headaches and tired eyes which the whole family suffer from, are caused by bad lighting. Karlík improves his grade with this work and goes off with his mother for the holidays. After their return they are pleased to find that father has bought new lighting for the whole flat. (According to the censorship licence)
According to the film yearbook issued at the time film was made, the length of the film was 350,0 m.