After a short ride, the doors opened on a corridor stretching off into the distance. This had very much a public-area kind of feeling, and my confidence increased as I progressed. At the end of the corridor, the space opened up to some kind of vestibule or maybe train platform. Along the far wall were a series of evenly spaced, identical doors, looking something like airlocks. Between each set of doors was a card reader panel. At a loss as to what else to do, I pressed Natasha’s card against one. A voice spoke into my ear. "Destination?"