There he meets the sweet-natured Nurse Mary Fletcher-Brown (Miranda Richardson), who helps George write letters to his relatives.
Darling shows up and, after expressing his lack of confidence in Blackadder's abilities, finds himself tied to a chair under intense interrogation.
Edmund says that Mary herself is the spy, a fact he verified over their time together (through, among other factors, her proficiency in German and her inquisitions into British tank movements).
Melchett rewards Blackadder by making him the head of Operation Winkle, denounces Darling as a "complete arse," and he and Smith leave to watch Mary's execution.
George enters the room and unwittingly reveals himself as the leak when he remarks that the relative he has been writing to is, in fact, his uncle Hermann in Munich.