René is in his larder, sampling cheeses for the café. Meanwhile, Michelle calls for an urgent meeting in the backroom. When René comes up from the larder, he, Edith and Yvette goes in there, while Mimi looks after the bar. Michelle tells the café gang that they are no longer trying to send the Enigma machine to London. Instead, the experts are coming to France, to examine it. The two experts will be dropped by parachute, be disguised as policemen and wiggle their batons in a special way, as a secret sign. As a reply, the café gang are to light a red lamp in Fanny's bedroom window. When the experts have arrived, one of the resistance agents, disguised as a Spanish accordion player, will deliver the machine.
General Von Klinkerhoffen has gathered the other officers (colonel Von Strohm, lieutenant Gruber and captain Bertorelli) and Helga in the colonel's office. He informs everybody that Berlin has decided, that if the Enigma machine is not found and returned within 24 hours, the general will be sent to the Russian front. He has, on his own, decided to send the others to the suicide squad of the Afrika Korps before he leaves. He orders the officers to find the machine and if it is not found by the same evening, the six most prominent peasants in Nouvion will be shot in the town square. When the general has left, the colonel decides that at eight o'clock that evening, they will arrest everybody at the café. Gruber does not like the idea and therefore, the colonel confiscates his uniform and confines him to his office, so that he cannot go to warn the café gang.
Edith, Yvette and Mimi are captured and brought before herr Flick. He orders them to take off their clothes - except Edith. Then, Von Smallhausen brings him a kettle with hot water, which he pours into three cups. Herr Flick makes tea by using what he claims to be a German invention (invented by Bern Von Tetley) - a teabag. When they drink it, herr Flick reveals to Von Smallhausen that the tea contains a truth drug, made from the sweat glands of the Patagonian fruit bat. Herr Flick asks them their names and they answer truthfully, which would indicate that the drug is working. When he asks them their ages and Mimi answers "18", Yvette answers "19" and Edith answers "nearly 27", he finds that it does not work and releases them.
When René opens the café, he meets officer Crabtree in the door. He tells René that the girls have been kidnapped by the Gestapo. A few moments later, they return and tell René that it is true that they were arrested, but that they revealed nothing. The only affect is that Mimi is behaving a little strangely, by having a strong desire to eat fruit, making squeaky noises and wanting to hang upside down. They take her into the kitchen, so nobody will see her and get suspicious. As the customers are entering the café, two of them turn out to be the British airmen, who sit down to have a drink. Yvette manages to get them upstairs, by showing them her legs, just in time before several German soldiers enter the café.
One of these soldiers turn out to be lieutenant Gruber, who is wearing Helga's uniform and even one of her wigs. He tells René that if the Enigma machine is not returned within half an hour, René will be shot. The next moment, Helga approaches the café, dressed in a helmet and a big cloak. René hides Gruber by letting him sit at a table, holding up a menu in front of his face. Helga shows René that she is wearing nothing but rather sexy undergarments underneath the cloak and she suspects Gruber of having stolen her uniform. René lets her sit down with a menu in front of her face too.
As Edith comes in from the kitchen, René explains the situation to her. The next moment, Yvette rushes down the stairs and tell them that two policemen are approaching the café. René thinks they are going to arrest him, but when they enter, speaking the same mangled French as Crabtree and wiggling their batons in the special agreed way, they realise that they are the British experts who have come to look at the Enigma machine. While Yvette is sent into the kitchen to get Crabtree, Edith goes upstairs to put the red lamp in her mother's bedroom window.
Crabtree comes in, giving the other policemen the secret baton signal. When Fanny has been downstairs complaining about the red lamp, a fourth policeman (Michelle in disguise) comes in and also gives the signal. She then tells them that the Enigma machine is approaching, disguised as an accordion. The next moment, monsieurs Alfonse and LeClerc enter the café, disguised as Spanish accordion players. They play a serenade to Helga, but when the German officers, including the general, enter the café, René flees into the kitchen and Crabtree tells them to stop playing. He then "arrests" them and all the "policemen" take the "accordion players" into the backroom, where the two experts examine the Enigma machine.
Meanwhile, the officers discover Gruber under his disguise. They also find Helga in her disguise. René tries to sneak out, disguised as Henri de Toulouse-Lautrec, but the general immediately sees through this disguise. He arrests René and orders the colonel to take him outside and prepare him for execution. Herrs Flick and Von Smallhausen show up and at gunpoint, they force the general and everybody else to stay in the café. Herr Flick points his gun at the general, who points his gun at herr Flick. When Von Smallhausen points his gun at the general, he is outmanned by two to one and nobody on "his side" has any gun to keep the balance. Helga even takes off her cloak to show that she is unarmed.
To break the standstill, Crabtree and René come out from the backroom with good news. René tells the Germans that the resistance have "thrown the Enigma machine into his backroom" and thus, it can now be returned to them. Edith brings it out and the general takes care of it. The Gestapo officers, who cannot take credit for having found the Enigma machine, grumpily leave the café and soon after, the German officers also leave, to have a drink at the chateau. Then, the café gang close the café, in order to celebrate too. They are interrupted by a knock at the door. When René opens, he finds Mimi outside, hanging upside down in the doorway.
- Note: In this episode, Edith's full name (Edith Melba Artois) and Yvette's surname (Carte-Blanche) are revealed.
- Note: This episode marks the last appearance of Jack Haig as Roger LeClerc, since Haig would die a few months later, before the beginning of series 6.