The train is segregated: the front cars have all the luxuries, the middle ones help run the train, and the overcrowded tail end houses castoffs. You can tell they're oppressed and angry because they look like they wandered off the set of Les Miserables. Curtis (Chris Evans) is planning a revolt, and his fellow sub-economy passengers are ready. Minister Mason (Tilda Swinton) and a small army stand in their way. What follows is a march/rampage forward through cars that showcase our species' absurdities, insanities, and cold calculations.
Snowpiercer is heavy on the allegories, with the bad guys repeatedly giving speeches about maintaining the hierarchy. But they're balanced by the great cinematography, intense action, and fantastic set designs. Inequality is the main theme here, with the train representing the system that keeps a select few in comfort while the rest are left to fend for themselves. Authoritarianism, indoctrination, decadence, and redemption are also handled as Curtis and his crew battle their way to the car that houses the "sacred engine" and its maker. The themes are so dominant that the cast members aren't playing characters--they're archetypes, acting out a narrative that we know, although in a way we haven't seen before.
And the end of the story, while predictable, blends bleakness and hope in a way that stays true to the film's dynamic. Snowpiercer is a unique take on an increasingly common type of fiction (post-apocalyptic), and it's well worth a look.
TL; DR: A thoughtful, thrilling sci-fi film.
This post to you by brownies. Brownies: heck yeah!