Much grumbling has commenced about the lack of promotional weight allotted to Children of Men, and every bit of it is justified; the movie crams a fascinating sci-fi premise into acutely crafted action tropes without sacrificing its livid virtuosity. That it should receive such muted publicity goes beyond being an unfortunate fluke, or forgivable byproduct of end-of-the-year overload: It's a crime against art to suppress this accomplishment, a great work but also an important one.

Director Alfonso Cuaron, who last made headlines for helming the third entry in the Harry Potter franchise, realizes British author P.D. James' nightmarish 1992 novel as a surprisingly cogent fable: Set in the fairly foreseeable future of 2027, London has decayed into a Third World war zone, wrecked by the tyranny of totalitarian rule and violence-prone homeland security. Mankind at large faces a bigger problem -- namely, its survival. No woman has given birth in the past 18 years, and ongoing terrorist attacks are shrinking the already endangered populace. Progressive minds are forced to simultaneously mine survival methods and ponder ways to bring forth a fresh generation. Eliminate the futility of babymaking and the concept is reasonably topical; Children of Men, a story about infertility, also offers fertile ground for able minds.

This is cinema writ large; it even boasts movie stars to help elucidate its grandiose ideas. Clive Owen, besting his engaging performance earlier this year as a crook in Inside Man, plays a former political protester named Theo. Owen comes across as the weary, uncomfortable inversion of Daniel Craig's James Bond, unwittingly forced back into action when his fierce former love interest Julian (Julianne Moore) comes calling. The couple's halcyon days are long gone, and the radical redhead now controls an underground terrorist faction inexplicably called "Fish." After a rough start involving, among other jolting twists, a violent police raid and one heartbreaking casualty, Theo overcomes his reluctance and joins the group, who require his assistance in the safekeeping of a young woman (Clare-Hope Ashitey). The plotting takes off when he discovers the point of the mission: The live cargo is pregnant.

Talk about having the weight of the world on your shoulders. The primary conflict of Children of Men becomes immediately and strenuously involving, especially once Theo realizes that a terrorist stronghold might not be the best place to raise the only infant on Earth. When they hit the road with an incoming baby in tow (with assistance from a stoner buddy brilliantly conceived by Michael Caine), the script draws a strong contrast between Theo's confidence in authority and the anti-establishment mindset of Fish operative Luke (Chiwetel Ejiofor, another actor one-upping his Inside Man role), and potential friendships are compromised by conflicting ideologies.

The pacing is consistent, thanks to Cuaron's genius direction, with integral assistance from cinematographer Emmanuel Lubezki. Again and again, action sequences thrill with gloriously fluid long takes that deserve a second, third or fourth viewing to be fully appreciated. Lubezki, who used natural lighting to convey the gorgeous, organic aura of Terrence Malick's The New World, here displays a knack for working miracles with a Steadicam. The most amazing accomplishment of Lubezki's extended shots is how much of the story is allowed to develop before edits interrupt the flow. Cuaron uses this striking technique to show us the acute attention required in any attempt to comprehend chaos; by pointedly not cutting to a new angle, he forces viewers to keep their eyes wide open. And no wonder: "Infertility [stands] as a metaphor for the failing sense of hope and the lack of connection within a generation," Cuaron told one interviewer. Look closely and you'll find that Children of Men is not just a parable for the present state of affairs -- it's the activist achievement of the year.