Colditz TV Series S1/E8 • The Traitor

Several escapes that should have worked end badly, with Ulmann waiting for them in hiding spots along the way. Suspecting an informer, Colonel Preston asks the other Senior Officers to interrogate their contingents. His suggestion is met with scorn, but he proceeds to interrogate the British and the others grudgingly follow suit. The perpetrator is caught: a Polish officer whose family was threatened with torture by the Gestapo. The Poles court martial him and condemn him to death, despite the extenuating circumstances. Colonel Preston tries to get him reprieved, with the help of the Catholic Priest, but to no avail. Finally, he goes to the Kommandant (reminding him that the Germans are entirely responsible for the current situation) who sends Ulmann in a race to rescue the Polish traitor.
(This episode was drawn from the real-life events involving Lieutenant Ryszard Bednarski, a Polish army officer in Colditz who turned informer apparently after the Gestapo threatened his family. Though the court-martial did in fact take place, in reality the Polish Senior Officer requested the Colditz commandant to remove Bednarski from the camp; Bednarski survived his imprisonment but committed suicide after the war upon meeting a fellow Colditz prisoner in Poland. The incident also inspired a subplot in The Colditz Story.)