The world has frozen over, and the last remnants of humanity are aboard a super long and advanced train (the titular "Snowpiercer") which circumnavigates the globe. The main problem is that while the front of the train is full of luxury and the upper class, all those crammed in the tail end of the train are treated as third world garbage. As with most oppressed people this is the tale of their revolt, to be more than what they are.
This is one crowded train.
I'd eagerly watch this again at the drop of a hat, and give it four doors out of five.