An out-of-work musician is desperate for work and when his best friend sees an add requesting a cellist he signs him up. However, the work is for a female, so he creates the character Märta Letterström and joins the trio at a small-town hotel. But being a woman is not as easy as you think.

Sture Letterström and Kurre Svensson take on the task of rescuing a secret document during World War II from a group of Swedish Nazis. Since both of them are known by the local Nazis, Sture takes on the role of Miss Märta Letterström, and Kurre also has to make use of his feminine side as well as a dress.