The horror sequel "28 Weeks Later" has the most arresting, gruesome and unnerving opening 11 minutes in recent moviegoing memory.

The follow-up to "28 Days Later," in which the United Kingdom was devastated by a virus that turns people into flesh-devouring zombies, begin by flashing back to something we never saw in the first film -- the clamor and terror of the epidemic in its first stages.

New franchise director Juan Carlos Fresnadillo (replacing Danny Boyle) briefly and economically introduces us to a small clutch of panicked citizens, walled-up, "Night of the Living Dead"-style, in a remote farmhouse. Soon enough, bloody-eyed virus victims pour in and slaughter everybody who isn't able to beat them off with a crowbar or outboard motor.

It's an epic intro to what, sadly, turns into little more than a frenetic killing machine. The new film is telling in its grasp of human nature, but illogical and utterly incapable of embracing the humanity it wants to show us. It reduces the best horror franchise of the new millennium to another heartless (and mindless) Hollywood splatterfest.

That heart-stopping prologue's wrenching climax beautifully sets us up for a grim tale of survivor's guilt as poor Don (Robert Carlyle) makes a break for it, abandoning his wife, Alice (Catherine McCormack), to a grisly death. Since the couple's two children were out of country when the epidemic hit, Don must contemplate explaining to them his cowardice after the "repopulation" of London begins.

The kids, poster-pretty Mackintosh Muggleton and Imogen Poots, are trouble from the moment they're brought back into "The Green Zone," the London resettlement area guarded by U.S. troops. They get a version of how Mom died from Dad and promptly sneak out of the Zone to collect stuff from their old house -- where they find that Mom is still alive.

Alice carries the virus, but she's survived the disease. Maybe Army doc Scarlett (Rose Byrne) can find a cure. Only, before that can happen, guilty Don and forgiving Alice share a smooch, whereupon Dad gets infected, loses it and promptly undertakes to paint Green Zone red. Oops.

The Army decides to "cleanse" the city, and the situation looks grim. The only hope of getting to safety for the doc and the kids is the aid of an Army sharpshooter who grows a conscience and starts popping off the servicemen attempting to carry out the purge.

The big, all-encompassing message of "28 Weeks Later" is that human nature -- compassion, empathy, a mother's urge to save a child -- is fatal. If it's a modern-day metaphor for the West and the Middle East, then movie that comes out on the side of genocide. Sympathy is weakness. Empathy -- for children, innocent civilians, parents and your own offspring -- will get you killed.

And forget the movie's jaded attitude about the coarse and callous U.S. Army. What soldier starts shooting his comrades on a whimfi

The effects are simple -- a set piece involving an unarmed helicopter being used against the living dead, the vivid napalming of central London -- but stirring. The best of them is the simplest of all, the shots of a ghostly city and countryside that recall the spooky opening of the first film. The silent skies are clear of planes, birds and pollution. Streets are littered by abandoned cars and pizza delivery scooters, with only the occasional skeleton to spoil the view.

The sequel takes the story even closer to the bleak heart of the film's obvious inspiration -- "The Omega Man." But the plot is absurd in the extreme, as chemical weapons are survived by holding a shirtsleeve over one's face; characters take every opportunity to go into tunnels and dark places; and raging, demented Dad is still clever enough to track his kids hither and yon with a notion of ripping their flesh and making them just like him.

We watch. We endure. Because, we hope, perhaps he'll stop spitting blood and growling long enough to tell the brats the line we long to hear, from the 30-minute mark to the finale: "This is all your fault."

C-

28 Weeks Later

Director: Juan Carlos Fresnadillo

Cast: Robert Carlyle, Rose Byrne, Idris Elba, Catherine McCormack.

Running time: 1 hr., 39 min.

Rating: R for strong violence and gore, language and some sexuality/nudity

Location: Opens Friday in theaters everywhere