The Undefeated
Following the British retreat at Dunkirk in 1940, Captain Pat Grant is one of many Allied soldiers captured by the Germans and sent to the prisoner of war camp at Laufen Castle. He is determined to escape and tunnels his way out, disguising himself as a townswoman. However he is recaptured after several days and sent to Colditz Castle, another prisoner of war camp from which escape is allegedly impossible.