12-year-old Edek comes to his aunt Hela, who lives by the lake, for holiday. He meets Monika there. Fascinated by the girl, Edek seeks her company. Near aunt Hela’s house some tourists come to stay. Monika befriends their son, Alek. Elegant and proud, Alek irritates Edek and his friends. At the first opportunity they start a quarrel during which Monika’s secret is revealed.