The meticulous Fabin Bom is called up for military service in the airforce.
The sisters Britta and Ellinor live with their grandfather, music professor Libergius, teacher and leader of the city's orchestra association. In the city there is also a youthful jazz band - to the professor's horror.
The fishermen Österman and Sjöberg are sued by merchant Wikström. In order to raise capital, they decide to start producing a medicine from a recipe by Österman's father.
