René is trying to keep his affairs with his two waitresses secret from his wife. In addition, the Communist women-only Resistance members are plotting against René for serving Germans and working with the Gaullist Resistance. The only reason that they do not shoot René is that their leader is in love with him, a fact he has to hide from both his wife and his waitresses. Furthermore, the seemingly gay German Lieutenant Gruber is also continually flirting with René.

Rene's death at the hands of a German firing squad was faked in an early episode, and throughout most of the show's run, he has to pose as his own twin brother, and to convince his wife to marry him again in order to regain ownership of his cafe. In the meantime, René's wife is wooed by Monsieur Alfonse, the village undertaker, who is torn between his love for her and his admiration for René whom he considers to be a true hero of France.

These few plot devices provide the basic storyline throughout the entire series, on which are hung classic farce set-ups, physical comedy and visual gags, amusing accents, a large amount of sexual innuendo and a fast-paced running string of broad cultural clichés that are reminiscient of Monty Python. Each episode builds on the previous ones, often requiring one to have seen the previous episode in order to fully understand the plot. At the start of each subsequent episode, René would summarise the plot to date to the 4th wall in a gag based on the "As you remember..." device commonly used in serials. In re-runs, local TV stations have shuffled the episodes, making the plot synopses useful.

The show's premise was not to make fun of the war but to spoof war-based film and TV dramas, and in particular a BBC1 drama about the resistance movement Secret Army, which ran from 1977 to 1979, and dealt with the activities of resistance workers based at a café in Brussels, though some inspiration was also drawn from patriotic black-and-white British melodramas of the 1940s. The French village setting is reminiscent of 1972's Clochemerle.

With four different languages (French, German, Italian and English) spoken by the characters, representing this to the audience could have been tricky. The programme uses the device of representing each language with English spoken in a theatrical foreign accent.

For example, an exchange between French-speaking characters, conducted in English with a French accent, is totally incomprehensible to the English airmen until Michelle switches to Bertie-Wooster-esque "top hole, old chap"-style banter in an upper-class English accent. The English undercover officer Crabtree, in the permanent disguise of a French-speaking gendarme, speaks abominable French. His mangling of French vowels is represented by similarly distorted English, most famously his customary greeting catch phrase of "good moaning"; many of his distortions come out as innuendoes, such as "I was pissing by the door, and I thought I would drip in". Curiously, in spite of the difficulties in communicating with the English characters, the French, Germans and Italians all appear to understand each other's languages perfectly (With the notable exception of Crabtree).

The last few series introduced a new gag, where Colonel von Strohm and Lieutenant Gruber are put in situations where they have to speak in a strange manner. In one episode, the two try to learn Spanish, which is basically "German" with high pitched voices and mangled consonants. In another they are forced to wear "suicide teeth" – large bulky dentures containing poison. This makes them garble their speech in order not to release the poison.