If you're looking to get severely stressed out for a couple of hours this weekend, you couldn't do much better than with this sequel to the tense, nasty, smart zombie-pic variant, 28 Days Later. While not quite as startling and cohesive as the 2003 Alex-Garland-written, Danny-Boyle-directed scarefest, it's still a gruelingly tense, deftly plotted, and slyly intelligent piece of work. And also it's really really disgusting.

Doyle and Garland return to watch over their franchise as exec producers, turning over the writing chores to a four-man team led by director Fresnadillo, who made an impression with 2001's life-is-a-gamble thriller Intacto. The setup here is as simple as the title. It's 28 weeks after the "rage" virus that turned much of England into screaming, blood-vomiting, fast-running zombie-like killers has been putatively wiped out, and a military force, made up of largely U.S. troops, is overseeing the reconstruction and repopulation of the no-longer-green-and-pleasant land.

Well, actually, much of it is still green, as we see in the harrowing opening sequence, which takes place at the time of the first film and shows would-be hero Carlyle copping out on wife McCormack during an attack so thoroughly terrifying that you can't really blame the guy. The return of those lucky enough to be visiting abroad when the virus hit reunites Carlyle with his kids, played by Poots and Muggleton (and I know I'm not the first person bemused by two actors whose names sound like characters out of Harry Potter playing brother and sister). Boy, is their sit-down about what happened to Mum ever awkward.

Things get even more awkward when it turns out Mum is in fact alive and relatively well, despite having suffered zombie bite. Military medico Byrne sees a chance to cure the virus here, but then things go from awkward to apocalyptic as zombie fury is unleashed once more, the U.S. led forces start killing everything that moves, and Byrne has to protect the two kids — with help from some initially reluctant soldiers (Renner and Perineau). Not helping matters is Carlyle's transformation from a decent, conscience stricken dad to something like his Begbie character in Trainspotting on steroids. Bad steroids.

Besides all the stresses and scares the picture offers some piquant commentary on the World As it Is Today; in some respects it can be seen as a thank-you note to America, for how well it handles overseas crises and foreign populations, and whatnot. But the analogs to certain international quagmires don't bog down the brutal momentum and doom-laden logic of the storyline, and 28 Weeks Later shows some serious stones in pretty much overturning the hopeful ending of the first film. True, Fresnadillo and company do start piling on the techniques and tactics in the last third — if you liked the hand-held camera stuff, wait'll you see the entire sequence shot through a night-vision scope! — but most viewers will likely be too caught up in the chase to be irritated. Either that, or they'll be hiding under their seats.