Bong Joon-Ho’s Snowpiercer has been praised for its action-movie spectacle and its message of class struggle. It exceeds expectations on both counts. Amid tightly-paced sequences that eschew standard-issue Hollywood pyrotechnics, it evokes some of the thorniest dilemmas of socialism and revolution, in the twentieth century and today.

This is a science-fiction adventure set entirely on a train. Or rather, the train, which forever zooms around the planet carrying the last remnants of humanity because the outside world has been rendered uninhabitable. The class hierarchy within the train is expressed physically: the closer you are to the front of the train, the more opulent and leisurely your existence.

The script, written by Bong and Kelly Masterson, takes the central conceit of the train from a decades-old French graphic novel of the same name, though the plots of the two stories are quite different.