This comedy is about one average family. The father works as master in the factory and his son is studying on high school. One day father must start to visit the evening school. It's the same school as his son visiting. The lives both students are connecting together. The son must teach the math and physics his own father. The father getting to know, that the life of the students is not simple as he supposed.

To Moscow have arrived the participants of the international conference of the zoophilologists and also the international jury which is to elect for the world festival the best performance of the program of Moscow circus. Mrs Whistler (Iva Janzurová), British associate professor, makes her understood with the animals in their language but the Czech professor Ruzicka (Jirí Sovák), though he is capable of using the animals language, prefers teaching the animals the human language. Ruzicka's friend, the poodle Archibald, speaks "in Human" very well. The scientific dispute ends with a bet - if Ruzicka teaches the circus elephant to sing, Mrs Whistler will eat up her hat.

Petr Rynes (Svatopluk Matyás) is celebrating his forty-fifth birthday in the company of his friends. He is happy with his wife, and his abilities at work have been rewarded with the medal For Outstanding Work. But a few short seconds are enough to change his life when he makes the ill-judged decision to take his car to bring a friend's wife to the celebration, and hits a pedestrian on the way. He has of course been drinking at the party and is consequently sentenced to sixteen months in prison. Being in jail is not an easy thing for a honorable communist. He soon gets into conflict with several violent inmates, who think they can break his spirit by violence.