Fascinating program.
The premise is that seven years ago, Earth became a frozen wasteland, brought about by efforts to reverse global warming. Boy, did the scientists get that wrong! In preparation, a brilliant (but eccentric) billionaire designed and built a perpetual motion train to house humanity. The train (1,001 cars long) travels around the world 2.7 times a year. The series focuses on the passengers--from the very rich, at the front of the train, to the dregs of humanity at the rear.
In this tight environment, you have the setup for class warfare, injustice, crime and punishment, and conniving politics while everyone tries to survive.
One of the things I didn't catch (or it wasn't explained) is who built the tracks the train travels on. Was it the billionaire? How did the tracks cross over large expanses of water (like the oceans)? Another question is how were the people chosen to get on the train? Did the rich buy their way in? How did you get a ticket? There are scenes of masses of people trying to get on the train before it left the station. What happened to them? Did they just freeze to death?
I've never written a dystopian thriller. Never really wanted to. I prefer happy-ever-after or happy-for-now stories. (Just call me Pollyanna.) The horrible things people do to each other when civilization breaks down upsets me. I cringed while watching movies like The Book of Eli or Blade Runner.
Yet some post-apocolyptic stories are thrilling and full of hope, for example The Hunger Games, Divergent, the Terminator series, and The Matrix. As I watch Snowpiercer, I hope the revolutionaries will take back the train and form a democracy. (See, there's the Pollyanna coming out.)
If you plan to write this type of story, you would do well to watch dystopian movies (better yet, read the books) and check out common themes.
How many different ways will Earth be destroyed? How will humanity survive? What would you do to survive?
