Henry the Green Engine is being a little stubborn shit, that’s what. He doesn’t want to get wet (It’s raining! The horror!) so he throws a train fit and sequesters himself in a tunnel. His driver gets mad at him and they argue for a bit. Meanwhile, the Guard shows up, blows a whistle a lot, and Henry blows steam at him in protest. (Either Henry kind of sucks in general or is throwing a temper tantrum. The jury is still out on that one.)
This entire ordeal is based on Henry wanting to keep his paint job pristine, by the way.
A fancy dude appears, this one named The Fat Controller. He is not a train, he is a human. This guy