Mismatched travellers are stranded overnight at a lonely rural railway station. They soon learn of local superstition about a phantom train which is said to travel these parts at dead of night, carrying ghosts from a long-ago train wreck in the area. The travelers eventually get to the bottom of the things that go bump in the night. In between the scary bits, comedian Arthur Askey plays the gags with his Vaudeville style humor, to the constant irritation of his fellow passengers.

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.