Suspecting a security leak at Stalag 13, General Burkhalter goes fishing with some false information and Colonel Hogan falls for the bait. As a result, Burkhalter plants a spy among the prisoners to expose the guilty parties.
A German oil refinery is so heavily protected that allied bombers have been unable to destroy it. So, Colonel Hogan decides that the only way to fool the gunners is to use a German plane.