The film follows a dress rehearsal of a charity concert.

The musical comedy tells the story of two friends about Usko and Toivo, both of whom happen to have same surname, Lahtinen.

A radio reporter from Helsinki arrives in the village of Kankkula just before Midsummer to conduct interviews. The old sheriff demands that his nephew Lauri, who serves as the village policeman, continue the generations-old tradition of arresting the old master of Tippavaara, whom the sheriff believes to be brewing moonshine. However, Lauri is in love with the old man's niece Leena, and the couple's plans to get engaged conflict with Lauri's duties.

Engineer Kallio, who is searching for uranium, arrives at the summer hotel owned by Director Lehtelä, accompanied by his assistants Joltinen and Pummi and painter Väinö. The manager's daughter Anni, his wife Mammi, and hotel employee Sirkka try to figure out the guests' secret identities.

Director Emil Rantamo goes with his family to the country for the summer. The family's son Fritsu gets engaged to Tipuli Niemi. Sausage maker Niemi thinks his daughter is engaged to the manager Rantamo himself.

At Pösökylä's lodge, Taneli injures her leg in fur hunter Eemel's wolf irons, and Eemeli decides to take up the position of lodge lodge. During the leave of office, Eemeli gives lessons to the rich Petter who rules the village and arranges the engagement of his daughter Ilona to the blacksmith Ilmar. At the same time, the affairs of the coffee bar owner Bertta are also put in order and the prisoner escaper Luukas is caught.

Eemeli, a lazy farm boy, is sent out into the world by his parents due to poor potato harvest forecasts. On his way to the logging camp, he meets Tommi, a man from Helsinki who sells razors and is headed to the same destination. At the logging camp, the loggers and Eemeli perform several musical numbers and flee from Isabella, the cook, who is hungry for men.

Eemeli leaves the countryside for Helsinki to obtain tax money for the bailiff who is pursuing him. In the capital, he becomes the assistant driver of Andersson, a cab driver. One night while driving, Eemeli meets Vesa and his little sister Jaana, whom Andersson and his granddaughter Katriina take into their family as foster children.

An idle work crew is ordered to go and heat up an abandoned house before it is demolished. A road sign pointing in the wrong direction leads them astray, and the men end up at an empty hotel, where they begin a program of evening entertainment led by Severi Suhonen.

'Tup-Akka-Lakko' is a sequel to 'Koeputkiaikuinen ja Simon enkelit' in which doctor Jyrä invented a test-tube-adult who looked exactly like Mutikainen, a mathematician. When the test-tube-adult's body emerged, his voice moved into Mutikainen's body because of the doctor's error. Problems ensue.