I suppose some might rational that it wasn't a one night pick up but an honest love affair-as depicted. But then that suggests this woman meant more to him than his wife-so maybe a one stand would be more accepted with respect to his family. The problem with the series is that she just disappears with a note saying she's going to Paris. Paris was still occupied at the time and we're left to wonder if she was killed, still alive, whatever?
While I thought the entire series was excellent there were several issues like the above that needed further explanation.