When newly weds Jack and Peggy face eviction, they are tricked into buying a run down houseboat. After rebuilding the engine, they take their friends Sid and Sandra, on a local trip down the river to Folkestone, but somehow they end up in France, and with no fuel and supplies, they resort to desperate actions to get back home.

The movie takes place during WWII. A dashing British RAF Officer is earmarked for a secret mission behind enemy lines in occupied France, but wishing to distract the enemy, enlists a person to double for him and thereby draw attention to North Africa . An unlikely airman is found and tutored in the ways of an English officer.