At the beginning of the Second World War, before Germany invaded Norway, a ukulele player in a British dance band playing at a Bergen hotel, is found shot dead during a radio broadcast of the band's show. It turns out he was a British agent keeping an eye on the band leader, Mark Mendes (Garry Marsh), who is suspected of being a German agent passing on information about British shipping to German U-boats, using a code concealed in the radio broadcasts.