When the Gestapo make a visit to the Stalag, they tell Klink they are looking for two guards that was transferred recently. One of the guards is on duty while the other, Captain Metzler, is on leave. The Gestapo go out and find the first guard and shoot him dead. Now they are waiting on Mitzler to return.
Hogan knows that if the Germans are killing their own men then Mitzler must have some valuable information. He goes and finds Mitzler and learns that both of the guards use to work in the German radio communication department. Mitzler has information about how the Germans broadcast information straight from Hitler's headquarters. Hogan has to get Mitzler out of Germany before the Gestapo finds and eliminates him.
There was a more serious mood in this episode as Hogan entire operation is revealed and then must be defended. In fact you can say this episode was must more of a drama than a comedy. Anyway the story was still interesting and the production top-notch. The only thing missing from this episode were the usual laughs.