28 Weeks Later 

• BLOOD SIMPLE Britain gets blitzed again in the second entry in the horror series obsessed with a multiple of seven.

When it comes to scaring an audience, sometimes simple is better. In 2002's 28 Days Later, a manmade virus called "rage" escapes from a lab and ravages the U.K. A single drop of blood infects you, and the afflicted instantly start vomiting blood and attacking their friends and neighbors. Twenty-eight days later, virtually everyone is dead or running around like they're on bad PCP trips, emitting echo-chamber shrieks. When the hero wakes from a coma, he finds London a wasteland worthy of T.S. Eliot.

That's it. No pseudo-scientific explanation, no government talking heads. Director Danny Boyle's apocalyptic thriller got its thrills from its simplicity, its strong script by novelist Alex Garland, and its grainy, antic visual style, with digital cameras swooping here, there and everywhere. It became a sleeper hit, and lo and behold, five years later, a sequel appeared.

In the way of sequels, 28 Weeks Later complicates things. The first film strongly implied the virus was unstoppable, with "reports of infection in Paris and New York." But Americans are apparently better at this containment stuff than the Brits. Seven months - yes, 28 weeks - later, Britain's infected have raged themselves out and expired.

The cavalry, in the form of a NATO force led by the U.S., returns to occupy the abandoned isle. A trickle of refugees is allowed to resettle a controlled zone in London, under the constant surveillance of wise-cracking soldiers. The first children to cross the Channel are a 12-year-old and his ethereal teenage sister, whose mom was a victim of the pandemic. Kids being kids, they sneak past the military cordons into a city where corpses still litter the streets. After the two make an unsettling discovery, an American military scientist becomes convinced their family holds the answer to stopping infection.

Wise-cracking soldiers? Scientists with theories? Cute kids? This sounds less like the culty 28 Days than Independence Day. But young Spanish director Juan Carlos Fresnadillo, who's taken the reins from Boyle, manages to deliver a doomsday movie that's anything but tame or mainstream.

Part of what was fresh about 28 Days Later was its sheer perversity. (One character speculates that the extinction of humans is merely returning the Earth to its normal state.) 28 Weeks Later takes those reversals of expectation and runs with them into territory that's pretty close to nihilism.

Along the way, it draws not-so-veiled topical parallels. The images of refugees returning to a wrecked city recall New Orleans. And the U.S. military conducts itself anything but heroically. After the virus inevitably resurfaces, snipers are told to shoot anyone who might be infected, with predictable results. Sure, it's all happening in London. But as in that other recent apocalyptic film, Children of Men, it's hard not to hear echoes of the "war on terror." Both movies are kinetic, harrowing illustrations of life in a war zone from the civilian point of view.

Unlike Alfonso Cuarón, the makers of 28 Weeks Later aren't above exploiting that violence for gory thrills. Their blur-whiz-blink-and-you-miss-it visual style makes it too easy to distance yourself from the carnage. By contrast with the first film, the characters here remain underdeveloped, hence not particularly sympathetic. The standout performance comes from Robert Carlyle, the scrappy Scotsman of Trainspotting and The Full Monty, as a guilt-ridden survivor. On the other end of the scale is Rose Byrne, poorly cast as a pretty twentysomething scientist named Scarlett - in Hollywood, is there any other kind?

Executive Producer Boyle has already announced a second sequel, 28 Months Later. It's hard to imagine he can stretch this franchise much further - 28 Years? 28 Centuries? Sooner or later, either the virus or humanity will bite the dust. But this sequel shows enough ingenuity to make the third installment worth a look.