A rich widow is found dead in her apartment in Helsinki due to gas poisoning. The incident is initially thought to be an accident, but inspector Palmu notices that the murderer made a mistake, and so Palmu, Kokki and Virta begin the investigation: who had come to the apartment through the balcony door and opened the gas tap while Mrs. Skrof was asleep?
Young sailor Arvi falls in love with a dance girl Kerttu in a Spanish tavern, who says that she is half-Finnish and wants to go find her real father.
A film centered around a popular Finnish song book. Young lovers Pirkko and Pekka break off their engagement at the end of an evening spent at a dance restaurant. At home, Pirkko finds a songbook in her room, whose songs turn into musical scenes. The night watchman carries the songbook with him, and it ends up, via a sad prostitute, a police officer, and a night shelter resident, with Pekka, who is waiting for Pirkko's forgiveness and comes to pick up his fiancée.
