At least the kids won't understand the implications.
A friend once described to me every Thomas the Tank Engine plot as, "Thomas doesn't listen to instructions and he gets in trouble." As a variation on the theme, this one is "Thomas breaks a promise and somebody else gets in trouble, and Thomas saves the day." This book is weird in that it brings up some worrisome questions. Seriously, I never really thought about the universe of Thomas the Tank Engine until I read this book. There's a scene where there's a train who is in a crate. They open the crate, "and his wood was worn and he had rust holes in his boiler." And he says "Surprise!" and they fix him up. What I want to know is: how long has that train been in that crate? Was he aware the whole time? That's like solitary confinement. That's horrifying. A kid wouldn't notice that, but I'm really disturbed by it, to think that this poor old train was just stuck, not being able to move, inside this box for god knows how long. I really don't understand this.
At any rate, people wouldn't actually get in trouble in this story if it weren't for the Troublesome Trucks, who apparently almost kill the other train, basically. I don't know if trains can die in this universe, but at the end he is "too weak to call out." So, if Thomas hadn't coincidentally found him, he would presumably have died from lack of fuel. I don't even know. What happens to a train in a situation like that? This book makes me think a lot more about this universe than I really ever wanted to.
There is a castle on the Island of Sodor, and an earl is fixing it up. An old train comes and the earl says, "I've got a special job for him. But promise not to tell him." And Thomas says, "I won't tell him," and then tells him. I guess all the trains are insatiably curious, because the train wanders around wondering what his job could be. He ends up getting shoved into a mine and trapped by a cave-in, but thankfully Thomas finds him and rescues him. In the process, the old train manages to find the lost crown of King Godred.