Two shot down pilots are in Stalag 13 and inform Hogan that allied planes are having a difficult time getting past German defenses to blow up a refinery. Hogan devises a scheme to use a German plane to blow it. The plan is complicated when Hogan discovers that the General who has the plane has made Hogan and his thinking a study of his.
Klink is caught in a conspiracy with Colonels Burmeister and Bussie to discredit General Burkhalter with the Gestapo. Burkhalter knows something is up and has the three arrested. Hogan is worried that a new Kommandant could replace Klink should he be found guilty. He must come up with a plan to get Klink back on the General's good side.
A milk maiden comes into camp selling milk and secretly sneaks a note to Hogan. He is to rendezvous with her at night in the woods. Hogan suspects a trap but meets her anyway. Hogan's suspicions are correct and she betrays him and hands him over to a Gestapo officer who knows all about Hogan and his operation. He wants one million dollars in diamonds or he will blow the whistle on Hogan and his men.
London airdrops a man codenamed Hercules near the camp. At the same time General Stauffen will be conducting an inspection of Stalag 13. Hercules' mission is to switch his briefcase with Stauffens. Stauffen is part of the plot to assassinate Hitler and Hercules' briefcase is equipped with a time bomb. Everything is proceeding as planned until Schultz unknowingly arms the bomb.
Hogan and his men smuggle a woman into the camp. Her name is Greta and she is a member of the Hammelburg Underground. She informs Hogan that his sabotage efforts in the area have the Gestapo whipped into a frenzy and that it is jeopardizing their efforts to smuggle out escaped prisoners. While this is going on, a Wehrmacht General wants to use Stalag 13 as a rest camp for Wehrmacht officers at the same time a Gestapo Colonel has designs on the camp as an interrogation facility for Hammelburg citizens. Hogan and his men play the two officers against each other while ...
Hogan manages to free four underground leaders from the Germans and smuggles the quartet into Stalag 13. But a plan to spirit the men off to freedom in England suddenly looks hopeless when a leaky pipe fills the gang's emergency tunnel with water!
All goes well when Hogan's gang steals Klink's code book from his safe, photograph the contents, and returns it to its proper place. But there's a small hitch - Carter forgets to load the camera with film!
When Newkirk discovers a new radio-controlled tank that could win the war for Germany, the allies want Hogan and the men to photograph the tank and then destroy it - but complications ensue during their mission.
"Tiger," a female underground agent, is arrested while trying to document some secret German bases and is held in Paris for questioning. So Hogan and LeBeau become stowaways aboard Klink's staff car and head for Paris to free her.
While trying to free the underground agent "Tiger" in Paris, Hogan must seek help from a Parisian fortune teller and also enlist the aid of a man who is a look-alike for Nazi Police Chief Heinrich Himmler!
With camp security raised, Hogan and his men are desperate to smuggle some top-secret of German fortifications to allies. The solution? Make liberal use of Carter's remarkable impersonation of Adolf Hitler!
The aristocratic Colonel Klink fails a routine physical exam and lands a combat assignment at the Russian front! Fearing a hard-line replacement at Stalag 13, the men must do all they can to rescind Klink's marching papers.
Hogan and his men make plans to lure Luftwaffe bombers within range of an allied anti-craft installation hidden in an abandoned warehouse, but Carter makes shambles of the plan when, while "leaking" the info to Klink, he forgets the name of the town where the strategic warehouse is located.
Suspecting a security leak at Stalag 13, Gen. Burkhalter goes fishing with some false information and Col. Hogan falls for the bait. As a result, Burkhalter plants a spy among the prisoners to expose the guilty parties.
An assertive Gen. Burkhalter "requisitions" the famous Édouard Manet painting, The Fife Player," from the Louvre museum in Paris to give to Hermann Goering as a birthday present. Undaunted by seeming impossible logistics, Hogan and LeBeau decide to steal it back!