Snowpiercer is an in-your-face metaphor for humanity hurtling toward climatic destruction on the rails of technology, a stratified society doomed to loop around an endless track in a metal tube isolated from nature. There are caricatures and stereotypes; the ridiculous decadence of the first class passengers is a bit over-the-top. However, the plot moves along quickly to a more meaningful conclusion. The most powerful scene is Chris Evans describing the first months of starvation on the train for the have-nots, a speech that will connect to an act of redemption. Warning: the hand-to-hand combat using primitive weapons is graphically violent, although not gratuitous; desperate people resort to what’s at hand to survive.