A truck delivers a new prisoner, Lieutentant J. B. Miller. Hogan finds it strange because there have been no raids recently. Miller says they were not hit; for some strange reason they just lost all power, fell out of formation, and were captured. He gives Hogan a code which clears him. He says there is another captured pilot, Major Martin, who is in Klink's office. They show Miller the coffee pot and proceed to listen in on Klink and Martin.
It is then that they learn that Martin is really a German agent, Hans Strasser. The mysterious fall out of formation was all Strausser's doing. Strasser says he has complete details of the next Allied offensive. He will meet intelligence at the Tempelhof Hotel to pass it over and wants a car from Klink. He also gives Klink the phone number of Herr Mayerink for verification. This is what Hogan needs for a phone tap. While Strasser is out cleaning himself up, Hogan and Miller go to Klink's office, where they start confusing Klink with silly stories that their own Miller is Hans Strasser and the phone number is a fake. As Hogan planned, this prompts Klink to call Mayerink, which they redirect to Newkirk and "Schimmel's Bakery." When Strasser returns, Klink has become convinced that he is really Martin and spinning him a big line about being a German agent. He throws Strasser in the cooler.
They uplift the information Strasser stole and find it is such top secret information that only someone high in the general staff could have passed it. London has been notified and is deeply alarmed. But they still do not know who the contact is. Hogan is sure Mayerink knows, and, posing as Strasser, goes to the German intelligence meeting. Carter goes as well, to take covert photographs. Mayerink introduces them to two others, Fraulein Kissinger and Herr Schneer. Hogan gives Mayerink the (mis)information from Strasser that will misdirect the German forces. They have several scrapes where their cover is almost blown, but Hogan manages to cover up each time. To his dismay, he learns that the contact is so high-placed that even Mayerink does not know it. Only Strasser knows, and he will not tell anyone except Herr Keppleman in Berlin.
Hogan goes to Strasser and, posing as Mayerink, arranges an escape to Berlin (all faked). Klink's office is rigged as Berlin headquarters and Carter impersonating Hitler in one of his temper tantrums. Klink has been drugged and out of the way, but Schultz almost wrecks everything by bursting in. Hogan manages to cover up. They put psychological manipulation on Strasser to reveal his contact, who reveals it is Medwin, the undersecretary on the war council. Strasser is returned to the cooler. Hogan is satisfied that if Strasser tries to tell Klink what happened, Klink will not believe him.