A spectral surprise

Given the short winter days this far north, I commute largely in darkness. The railway carriages are well-lit and variably heated. After I settled into my seat for my journey home this evening, I glanced around to see who else is around me. In the window, I saw the reflection of a lady a couple of seats ahead of me.

Curiously, looking in my actual carriage, I couldn't see her at all, she could be seen only in the reflection.

It turned out that there was a train at the platform alongside, I suppose she was seated on that one instead and I spied her directly. At least, we've now set off and I no longer see her!