Fifteen-year-old Jirina is spending her summer holiday with her father at the family cottage. The father has to go to Prague on business and, after few moments of hesitation, he decides to leave Jirina alone in the cottage. The holiday by the river is pleasant and the gang of children to which Jirina belongs enjoys it duly. Jirina is wooed by Roman, but she is more interested in Franta from the opposite bank of the river. Franta invites the girl to his cottage, but when the more experienced youth wants to kiss her, Jirina runs away. She at the same time finds out to her sorrow that Franta is still dating his love from last year's holidays, Bláza.