The Prague Grand Orchestra travels by train to a music festival in Yugoslavia. Only the singer Sona Klánová missed the departure. In the meantime, she managed to buy a ticket to Belgrade at the air-terminal from Mrs Navrátilová, who couldn't make the trip. In the meantime, the orchestra conductor is beside himself with despair. He phoned to Prague from the border, and when he realized that Sona had left her house in a taxi, he thought that she would catch up with them by the road. The orchestra delayed the train's departure with an improvised concert for the custom officers and the passengers.