It beeps more insistently and he will start feeling like he really needs to fly down and board the train. If he keeps ignoring it/fighting it then he will find himself waking up in the luggage compartment on day two with the honour of being our first in game death.

It is a little higher than the walls, but the fog is too deep to see anything beyond them. He won't be able to figure out why he can't get higher but it doesn't feel like a barrier as such.