At Stalag 13, a German prisoner-of-war camp, Colonel Robert Hogan and his fellow cohorts are a subversive group with many hidden talents. However, a spy has been planted amongst the men by the Germans.

Hogan's scheme to help a German baroness escape to London is thwarted by the arrival of a new prisoner of war, Colonel Crittendon, whose repeated, bungled attempts at escape are wreaking havoc on Hogan's mission to spirit away the baroness.

The Germans' plan to build a synthetic fuel plant at Stalag 13 would spell disaster for Hogan's men and their important strategic subterfuge. So, Hogan attempts to convince Klink that there's a massive oil supply under the camp.

When a British submarine cannot make a planned rendezvous to pick up a POW carrying an prototype of an important new German weapon, Hogan must come up with a sturdy, seaworthy replacement.