Hogan and Co are out at Weber's farm collecting information from Maria Hoffman, an Underground agent, on German forces in France. Then Carter reports a Gestapo car approaching. Fearing they have been spotted, Hogan and Co flee while Maria tries to stall the Gestapo, but she ends up captured. The Underground later confirms she is being held in custody in Hammelburg. Hogan resolves to rescue her, particularly with London wanting the rest of the information she is carrying. While Hogan tries to think of a plan, General Burkhalter and his sister Gertrude Linkmeyer arrive in camp. Hogan decides to kidnap Gertrude and exchange her for Maria.
Meanwhile, Burkhalter is under the impression that there is something romantic going on between Klink and Gertrude. Now he is trying to push them into marrying, saying Klink needs marriage. Klink is horrified at the idea and turns to Hogan for help, but Hogan offers him the same advice as Burkhalter. Eventually, Klink asks Hogan to go to Gertrude and ask her if she really is keen on the marriage idea. While Hogan is there, Gertrude receives a call (from Kinch) that Klink wants to see her at the Hofbrau the following night. Gertrude is not that keen on Klink but agrees to go. But on her way to the Hofbrau she is stopped and abducted by Hogan's men. They keep her tied up and blindfolded in the tunnel, and tell her she is in a hotel in Dusseldorf. They let her overhear things that let her think she knows her location.
Next morning, Burkhalter calls in Major Hochstetter over Gertrude's disappearance. The phone call comes about the exchange: Gertrude will be released 24 hours after Maria is, and there will be further instructions. Hochstetter finds it suspicious that it was Klink the kidnappers called. He refuses to exchange Maria, but Burkhalter demands it. Hochstetter is forced to agree after Burkhalter threatens to call Himmler over the matter. Hogan and Co are listening on the coffee pot and Hogan orders they contact the Underground to report when Maria is released. He also composes a romantic letter for Schultz, to entice him to meet one Wilma Braun at Weber's farm.
The Underground reports that Maria has been released. Schultz receives the letter, and is smitten. He decides to go out that night to meet Wilma with flowers and wine. But it is at Weber's farm that they bring Gertrude and secure her. They phone Klink's office to tell them to go to Weber's farm at 2200 hours, but not set any traps or it will mean disaster for Gertrude. But of course Hochstetter prepares his forces to catch the kidnappers.
Schultz arrives at the farm, but finds Gertrude instead of Wilma and unties her. Hochstetter and his forces arrive and surround the farm. Hochstetter demands that Gertrude come out first, and frakes the farm door to show he means business. Gertrude emerges, but before she can tell them about Schultz, they open fire again. Schultz emerges, with his wine and flowers ruined. Later, Gertrude gives Hochstetter the misinformation about the Dusseldorf hotel that Hogan's men gave her while she was blindfolded. Hochstetter is still suspicious of Klink, but Gertrude is convinced of his innocence. There are hints that she is beginning to fancy Klink.