Hogan and Co are out on a rendezvous with Underground leader, Oskar Danzig, in order to pass over vital military information for Danzig to relay to London. Danzig is a master of disguise and is particularly famous for his female impersonations (watch this). They pass the information, but as Danzig is leaving, a Gestapo patrol spots them and opens fire. Presumably, they have recognised Danzig as Hogan later hears from Schultz that Danzig is the latest top secret news among the military. Le Beau takes a hit and is rendered unconscious.
Back in the camp it is established that Le Beau only received a flesh wound and fainted from the sight of blood. But then Hogan receives word from the Underground that Danzig was not so lucky and is in urgent need of penicillin. It is vital that Danzig survives because London will only accept the information if it comes from him. Hogan arranges for London to drop some penicillin.
Meanwhile, Klink announces that he has been made honorary chairman for the fundraising committee for German soldiers on the Eastern front. He wants volunteers to help him host a tea party for the generals' wives. After some persuasion, Hogan and Co volunteer.
London makes the penicillin drop. But as Newkirk and Carter are retrieving it, the Gestapo patrol again spots them and opens fire. They escape, but the patrols are now too heavy for them to get the penicillin to Danzig. And with Klink also laying on extra guards because of the party, Hogan has to find another way to get someone out of camp to deliver the penicillin. And he must do it quickly, because news from the Underground is that Danzig's condition is worsening.
Figuring one more woman would not be noticed at the party, Hogan has Newkirk disguise himself as a woman in order to join in. The plan is for Newkirk to hitch a ride into town with one of the ladies and deliver the penicillin that way. But at the party, Hogan finds he has miscalculated - General Burkhalter does notice there is one woman too many. Having heard about Danzig and knowing his reputation for female impersonations, he gets suspicious. He almost calls the Gestapo, but Klink offers to mingle with the ladies and use it to unmask any impostor. But he ends up pulling off Frau Mannheim's wig in the mistaken assumption that she is the impostor (due to the bet that Hogan made with him). This embarrassment wrecks the party. Newkirk volunteers to drive the distraught Frau Mannheim back to her hotel. The other ladies walk out on the party, deeply offended.
Newkirk returns to camp disguised as an old man (courtesy of Danzig). He again meets the Gestapo patrol, but fools them with a 'deaf' routine. He tells Hogan that Danzig is now recovering.