Will Hay, back in his role as a hapless teacher, is hired by a grim school in remotest Scotland. The school soon starts to be haunted by a legendary ghost, whose spectral bagpipes signal the death of one of the staff. Hay, assisted by Claude Hulbert and Charles Hawtrey, has to unravel the mystery before he becomes the next victim.

Nazi spies are out to destroy a new submarine killer, the "Firefly", being developed by the British navy. A hapless waiter named George, after being rejected for military service three times, finally "joins" when, during an air raid, he is mistaken for a real sailor. He soon unwittingly stumbles into the secret hideout of the Nazi spies trying to destroy the Firefly. Complications ensue.

The Crazy gang invade Nazi Germany !! They accidentally pilot a balloon over enemy territory.