Sandra was always vague about what her job was in the British army and for good reason. I'm pretty sure she worked for British Intelligence perhaps as a spy. Remember her on the train in episode 8 when the German soldier asked her for her papers? She was dressed like a scullery maid. She responded in French and he looked at her papers before throwing them in her face. A couple of scenes later it showed her smartly dressed in a nice overcoat and heels, walking down the sidewalk, stopping to view the reflection in a mirror of a table of German soldiers across the street sitting at an outdoor table. She then entered an alley and then what looked like an abandoned building, all the while looking over her shoulder to make sure she wasn't followed. That's the last we see of her. I'm not all that curious about what became of her myself, no more than I would be any other supporting character we saw. Hers was not a principle role in the story and she was only in 3 of the 9 episodes. I chalk it up to "what happened to her is whatever you think happened to her".

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