Thanks all. That was a "lucky shot" - I was on my way to the next train and felt compelled to step back. I took several shots in a row, essentially waiting for the platform to be empty, but when I saw the two ladies... click.
I am at Gare du Nord twice a day, Mo-Fr, and this is the place in Paris I know best, alas. Of course photography is forbidden because of terrorism (?!?). As is smoking on the platforms. But everybody smokes, so...
