The science-fiction genre has often struggled with defining its identity, the genre plagued with high-concept action pieces that are ultimately lacking in substance.

On the other side of the spectrum are intellectual pieces that might not have the same entertainment value. "Snowpiercer" manages to find a satisfying balance between the two as it blends a highly intelligent and deep premise with innovative action.

The film is set in a futuristic ice age that has destroyed the planet. The survivors all board a train that is divided up into different social stratospheres. The poor live in the back of the train and are forced to submit to a totalitarian style government ruled by the train's creator Wilford (Ed Harris). Among those living in the back of the train is Curtis (Chris Evans) who, under the direction of Gilliam (John Hurt), has started a revolution to take control over the train and thus improve the living conditions for the poor. The journey through the train features some rather fascinating insights into the human condition while showcasing terrific action set pieces.

Korean director Joon-ho Bong's big battle sequences are heavily stylized and gory (almost bordering on overindulgent), but also full of wit. A big battle between the two factions midway through the film is unabashed in its violence, but the twists and turns throughout the sequence feature some rather comic timing, particularly with Tilda Swinton's Mason.

The film's plotline actually follows a number of characters. Curtis is the heart and soul of the film as his journey from a follower to a leader is layered with revelations that stop him from turning into a stereotypical hero. Curtis makes numerous decisions throughout that are not only questionable, but infuriating. It is clear that Bong wants to make sure the audience identifies with Curtis, but he wants to make the growth of this connection a difficult one. Later in the story, Curtis makes an essential revelation that only adds to this tension between the viewer and the character. Evans does a phenomenal job expressing the complexity of the character. His face remains rather steady in its expression throughout, almost as if trying to not betrayal the pain; he wants to give off the impression of being fearless. But Bong's close-ups allow the audience to engage Evans' eyes; these give away the inner turmoil wondrously. His steady gaze looks as if it were always haunted and remembering something.

The other major characters in the film are Yona (Ah-sung Ko) and Namgoong (Kang-ho Song). The two drug addicts initially imbue the morose tail with gags and perfectly timed humor. But as the journey develops and the death count mounts, the interactions between the two showcase a growing intimacy and weariness. The film's climactic moments actually hinge on these two characters more than they do on Curtis, thus layering the overall conflict of survival in an inhumane society.

Ed Harris takes a while to make his appearance as Wilfred, but he manages to completely subvert the notion of his character being the villain. For most of the film, the viewer is left with this impression of the "big, bad Wilfred" only to be left in utter shock by the calm, even and friendly demeanor of Harris' personage. In most of these Orwellian societies, the ruler is the villain that must be overcome in order to ensure freedom for all. The unraveling of the plot is not quite so simple in "Snowpiercer" and the viewer is left to ponder about how disrupting the balance of an established society (whether good or bad) could potentially damage all involved. The film's finale points toward a more positive perspective, but everything that comes before brings these simple answers into question.

The film is packed with a number of other terrific performances, most notably by Jamie Bell as Curtis' loyal sidekick Edgar. Bell's swagger contrasts sharply with Evans' more severe nature. Octavia Spencer puts her tremendous range on display in an ultimately short role, further establishing herself as one of the finest actresses of her generation.

"Snowpiercer" is not getting the wide release that other major science-fiction thrillers usually get, but it certainly deserves that and more. It manages to blend an engagingly complex premise with over-the-top action and brilliant acting to creating one of the more satisfying and thought-provoking films of the summer.