Ten-year-old David joins a sailing club. He trains hard and helps repair the sailing boats, but people have to take turns actually sailing. The club chairman Vala wants David to sail with his son Olda. Olda's previous team mate Béda has grown too fast, but with little David Olda could win a place on the regatta to Finland. Olda is arrogant and accustomed to winning with little effort; he bullies David and calls him "Greenhorn". He makes David his servant and blames him when things go wrong.
Brave sons of the king, twin brothers Jaroslav and Jaromír love and help each other. It was they and another brother - Jindrich, who once saw the portrait of Princess of Diamond Mountains, fell in love and went on her quest.
