Swedish comedy from 1940. Kurre Karlsson, a simple man of the people, will be called up for military training given by an anti-aircraft units at sea. He does not like the military and will do anything to get away. One day he steals a wallet and in it finds his paper suggesting that a spy is on the move who think stealing trade secrets about the weapons factory in Granefors.

Likeable country postman Harold Petts gets transferred from his village to London, where on his arrival he unwittingly foils a mail train robbery. Innocent in the ways of the big city, he is thought to be a member of another gang by both the train robbers and the police, who all suspect him of trying to rob the post office where he works.