Apparently, as the film "Zero Hour" inspired "Airplane!", this routine propaganda film, "Secret Mission" from 1942 was the inspiration for a British comedy, "allo, allo." The film stars James Mason, Roland Culver, Michael Wilding, and Karel Stepanek.
Mason plays Raoul, a member of the Free French Army (and his accent is appalling) who returns to France to get German intelligence. He brings with him Captain Red Gowan and Major Peter Garrett (Roland Culver and Hugh Williams). Raoul brings him to his family's home, which his sister Michele (Carla Lehmann) is not happy about. The three also enlist the aid of a Cockney (Wilding) who is married to the owner of a café.
The story is pretty absurd, though done with a straight face. First of all, Red and Peter walk around this French village in trench coats like no one is after them, and they stick out like sore thumbs. They bluff their way into German headquarters as champagne salesmen and these dumb Germans give them a lot of info about troops, and leave them alone in the commandant's office so they can take a look at the map and write down targets.
The saving grace of the film is that it focuses on a family and the effect of war, and there, it does a decent job. These films were meant to keep people going during the war. I'm sure at the time no one noticed the more amusing parts. Evidently someone did later on, though.
I'd call this mildly entertaining, and if you know the show on which it's based, you'll love it. Kind of like seeing Zero Hour after you've seen Airplane!