London radios Hogan with an urgent request to find information on a secret factory, its location and defences. As luck would have it, Hogan already has the information from the Underground. It is actually a secret ball bearing factory. But before he can send the details to London, an air raid strikes and destroys the radio. They must find another way to get the information to London.
Klink announces to Hogan and Co that they are going to be provided with some entertainment. They will be listening to a radio propaganda programme, Berlin Betty. Betty starts broadcasting over the loudspeakers and says that the prisoners of Stalag 13 are invited to snuggle up with her, etc, etc. But there is one condition - they must broadcast a propaganda speech for demoralising the Allied war effort over her programme. And Klink mentions something else to Hogan - Berlin Betty is broadcast to London every night.
Newkirk comes to Klink's office to say that he has accepted Betty's offer and he wants Klink to arrange the appointment. Klink is delighted to do so as he is angling for a promotion on this. Newkirk requests that this be kept secret lest the others will brand him a traitor. So when Hogan comes in, Klink tells him that Newkirk is giving the usual complaint about the food, which Hogan reinforces.
Hogan orders Newkirk to compose a speech that will incorporate their new code and the information about the factory. To keep appearances convincing, Le Beau simulates a fight with Newkirk because he is angry at his treason. Klink starts giving Newkirk VIP treatment and says Betty is coming to Stalag 13 to make the broadcast.
Betty arrives, and she is a beauty that the men, including Schultz, fall over. Betty likes Newkirk's speech and wants to talk to him privately about it. Of course this entails plenty of wine and kissing. The others are watching from afar through their periscope and get worried about Newkirk's resolve.
Then Betty tells Newkirk that she is being forced to make the broadcasts because the Nazis are holding her family hostage. Newkirk reports this to Hogan and is unsure about broadcasting the speech, fearing this will imperil Betty's family. The others are unsure too, especially after the kissing they have witnessed. Newkirk has to make a decision.
Eventually, Newkirk goes through with the broadcast. The others are listening over the coffeepot and are relieved. It is then that Betty tells Newkirk that she had lied to him. It was a trick she always uses to test the prisoner's sincerity, right down to the kissing. Newkirk gives her a wry retort over the phoney kissing before she leaves.
Afterwards, Klink calls Hogan into his office and shows him the citation he received as a reward from the Propaganda Minister. He sends Schultz out to get it framed. Just then, there is a roar of planes and then bombing that rocks Klink's office. A dishevelled Schultz comes in with a handful of ball bearings and says they are all over the camp. He holds up the citation, now peppered with holes from the ball bearings, and asks Klink if he still wants it framed.