1790 Turku. After Katarina Thorwöst becomes a widow, there are many suitors, but her heart belongs to the fencing teacher lieutenant Carl-Magnus Schildt.
The story is set in Helsinki's revue theater Punainen Mylly, run by Jalmari Haapala with Erkki Pajula as its lead singer. Between performances, dancer Kaarina and doctor Kalle are offered the chance for romance, despite some misunderstandings.
The S/S Vellamo heads to Alexandria with Kaarina, the daughter of the ship's owner Hallerman, on board. As Kaarina trades places with the family's housekeeper Marja, first mate Yrjö takes a liking to Marja whom he believes to be miss Hallerman. Meanwhile Kaarina, pretending to be a member of the cleaning staff, starts getting close with lower ranking officer Kalle Aaltonen.
