At the start of World War II, musician George Hepplewhite (George Formby) gets on a boat thinking he is on his way to Blackpool, but arrives in Bergen, Norway instead, where he is mistaken for another ukelele player. He then meets the desk girl at the hotel, Mary Wilson (Phyllis Calvert), who is a British undercover agent and thinks he is one too. The duo manage to find and break a code that the Nazis are using to sink allied shipping. (wiki)
