A boy and a girl enter through the door behind me. The boy sits in front of me, while the girls sits behind me.
After a while, the girl joins the boy in front of me.
After a while, both of them stand up and go through the door at the far end of the train car.
After a while, they come back in and pass through the door behind me. I notice the man behind me in the reflection in the partition half stands look at the empty seat in front of me. He is watching them. The train stops, and the man stands up and prepares to step up onto the platform. He assesses the car, and goes to step downstairs but accidentally approaches the up-escalator, and then moves on up the platform. Out of the corner of my eye, I see boy and the girl run forward and dart into my car again, and they find a seat at the far end, the absolute front of the car.
Through the window, I see the man pass me again. He seems to be looking for something, trying to tamp down his urgency. The doors close and the train moves on, leaving him on the platform.