纳粹间谍正在消灭由英国海军研制的新型潜艇杀手“萤火虫”。 一个不幸的服务员,名叫乔治,在三次服兵役之后,在一次空袭中被误认为是真正的水手时,终于“加入”了。 他很快就不知不觉地偶然发现了试图摧毁萤火虫的纳粹间谍的秘密藏身处。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.