The Karpísek married couple, both doctors, are leaving for London for two months on business. They entrust their five-year old son Jozánek (David Schneider) to the care of their neighbor, Mrs Pokorná (Slávka Budínová). Jozánek is not pleased with the arrangement. He would rather wait for his parents at the house of his grandfather (Rudolf Deyl), a ferryman in Kralovice. On the following day after his parents' departure, the boy runs away to join his grandfather. His journey proves more difficult than he had imagined, but with the help of kind people he finally succeeds.