Jaroslav Novák

Inspector Cadek from the 13th police station keeps an eye on the released safe-cracker nicknamed The Cat. He rightly suspects that Cat will go and pick up his last loot which the police didn't manage to find and that he will want revenge on Karta who helped put him behind bars. At the hospital, Cat's ex-lover Fróny hopelessly falls for doctor Chrudimský and decides to start a new life. She still refuses to help the inspector in his search for The Cat and Karta.

The young worker Helena Pokorná and her widowed father are employed in the same factory. The father is spending his holidays at home in Prague and is looking forward to work. Helena is to go to the seaside for a rewarding holiday. On a hot July day, the girl rides to work in a crowded tram. On the embankment, the crowd pushes her out and Helena fails to get into several other cars. Tempted by the river, the girl calls in sick to work. She takes a steamer to Modřany. There she meets a young man who wants to sleep by the river after his night shift. Helena is drawn into the strange pastimes by a group of notorious loafers and water girls.