About a half-hour into Alfonso Cuarón's dark tale of the near future, Children of Men, there's a sequence that begins with the film's reluctant hero Theo Faron (played by a suitably hangdog Clive Owen) being driven through the devastated English countryside to an undisclosed location. Also in the car are several members of the Fishes, an immigrants-rights organization that has enlisted Theo to help with its latest mission. These individuals include the group's leader--and Theo's ex-wife--Julian (Julianne Moore), her right-hand man Luke (Chiwetel Ejiofor) and a young black woman named Kee (Claire-Hope Ashitey) who they are trying to smuggle out of the country under the nose of the authorities. As they round a bend in the road, a rusted-out car comes careening down a hill and explodes in front of them. At the same time, an armed mob emerges from the trees and swarms their vehicle. Luke throws the car into reverse and drives wildly in the opposite direction, but he's pursued by two men on a motorcycle, who fire several bullets into the car, hitting one of the passengers and shattering the front window. Theo opens his door and knocks them off their bike, as Luke turns down a side road and guns the engine. They speed off, leaving the mob and the assassins in the rearview mirror. It's only after they've gotten away and you remember to take a breath that you realize the entire sequence was filmed in a single take.

Children of Men is filled with scenes like this one, which dazzle you with their technical complexity and visual virtuosity. On this level alone, it's easily one of the best films of the year and represents a new level of artistry for Cuarón. Set in the year 2021, the film imagines a future where mankind has lost the ability to reproduce. This development has plunged the world into chaos. England is the only country on the planet to still have some semblance of order, largely because its citizens have surrendered their freedoms in favor of (relative) safety. One of the first acts of the new regime was to round up all non-native Britishers and toss them into overpopulated detention camps. Not everyone agrees with this policy, though; militant groups like the Fishes are striking back at the government through bombings and other acts of intimidation. Then there are people like Theo, who are caught somewhere in the middle. Although he works for the government as a low-level bureaucrat, he doesn't support those in power. But his revolutionary zeal perished several years ago along with his young son Dylan, a victim of a flu epidemic. These days, Theo is happier to simply escape from the world by visiting his pal Jasper (Michael Caine), a '60s-hippie type who lives in a secluded house in the country where he grows some stellar pot.

Despite its sci-fi trappings, Children of Men is very much a companion piece to Cuarón's critically acclaimed drama Y Tu Mamá También. At its heart, this is a classic road movie where one man's trip across a country (in this case, futuristic England) represents his internal journey towards some kind of self-awareness. Not long after the aforementioned roadside attack, Theo discovers the truth about Kee (she's pregnant) and also learns that the Fishes intend to use her for their own ends. (Because she's an immigrant, they hope that her pregnancy will shame the government into reversing its "no foreigners" stance.) So he spirits her away in the dead of night and escorts her to the coast, where they are supposed to be met by representatives of the so-called "Human Project," an underground scientific organization that may or may not exist. It's through his grueling experiences on the road with Kee that Theo remembers how to care for a person and, by extension, a cause.

Children of Men actually improves on Y Tu Mamá También in many ways, particularly because Cuarón doesn't smother the proceedings in overwritten narration. This is an intensely visual story in which most of the important details about these characters and the world they inhabit are communicated through images rather than dialogue. In fact, the film is at its weakest when it tries to explain too much; some of the early conversations between Theo and Julian sound painfully expository. Once Theo sets off on his quest, however, Children of Men becomes both a white-knuckle adventure film and an emotional drama that makes a potent case against the anti-immigrant sentiment currently being expressed in England as well as in this country. Cuarón's carefully choreographed long takes grow increasingly more elaborate, climaxing in a stunning tracking shot that finds Theo pursuing Kee through a war zone as bombs and gunfire rain down around him. Children of Men is a film that demands to be seen more than once, if only to figure out how the heck the filmmakers pulled sequences like this one off.