The Mráz family is preparing for holidays. Parents are traveling to the spa and little Petr is going to the country to his grandparents. In addition, to the chaotic preparations, mother's friend is bringing a dog Blek. She wants Petr to look after it. Grandfather welcomes Petr and the dog with pleasure because he needs the ally against strict grandmother. Grandfather is not very skillful and thus grandmother often experiences troubles with his ideas.