Zombies. Everything is better with zombies. Let's be honest though: these aren't really zombies. Not in the coy Shaun Of The Dead way that the z-word is ridiculous but in the sense that they are something other. The disconnect is velocity. The tone is set by the opening scene. It starts off in familiar fashion, with Don (Robert Carlyle) and Alice (Catherine McCormack) barricaded in a surrounded house, but quickly evolves into a frenetic chase. These zombies are fast and their pace infects the film. Traditionally the fear in a zombie movie is that of a gradual, inexorable closing in of the walls, crushing a small band of survivors by increments. This is more akin to a plane plummeting to earth, trailing burning wreckage.

28 Weeks Later is the cunningly titled sequel to 2002's well-received 28 Days Later, written and directed by Alex Garland and Danny Boyle. Garland and Boyle were otherwise occupied creating the majestic cobblers that was Sunshine (although they still pick up an Exec. Producer credit here and long-term producer Andrew MacDonald was also on board). In their absence, the reins were taken up by Juan Carlos Fresnadillo, the Spanish director whose debut film Intacto is one of the best fictional treatments of the idea that luck is an empirical fact, and a team of his compatriots, most notably cinematographer Enrique Chediak.

The rage virus that infected Britain in the original film has burnt itself out. The contagion has spread to every available body and then, trapped by the country's coastal borders, the infected have starved to death. Now, twenty four weeks later, the Americans have arrived to set up a secure quarantine zone in the heart of London with the aim of re-patriation and, presumably, eventual re-population. Andy (Mackintosh Muggleton) and Tammy (Imogen Poots) are flown in from a refugee camp in Spain, where they had been on a school trip, to be reunited with their father, Don. Aged twelve, Andy is the youngest person in the country.

Not long after this everything goes into total bollocks overdrive. It goes without saying that the virus was not successfully eradicated. I will allow you the pleasure of picking apart the plot holes in its re-introduction for yourself but suffice to say it wouldn't have been any less plausible if the Americans had just installed a big, unguarded button labelled "PRESS HERE FOR ZOMBIES." In the context of the film though, this doesn't really matter. There are only two sorts of people in 28 Weeks Later: the infected, who want to bite everyone in the face, and the non-infected, who really don't want to be bitten. As such the plot can simply be compressed to "run away as fast as you can" without fear of losing vital nuances.

Those doing the running are Andy, Tammy, and two soft-hearted soldiers, Scarlet (Rose Byrne) and Doyle (Jeremy Renner). There is little resembling characterisation for this quartet, which might be just as well. Without wishing to be excessively classist you can get a pretty good idea of the performances of the two young leads from their first names, and it requires considerable suspension of disbelief to accept that these wooden stage school actors are the product of Carlyle and McCormack's loins. The best you can say of Bryne and Renner, meanwhile, is that they look just about plausible in their uniforms. (Don and Alice are the only proper characters; that they are discarded so quickly tells you everything you need to know about the film.) Throughout, the unmentioned elephant in the room is the fact that through their selfish actions Andy and Tammy are responsible for genocide. But there is no blame or ethical anguish, only the purity of survival. The film is almost defiantly anti-intellectual (which makes the supposed allegories to Iraq even more laughable), and rather than being cardboard cut-outs the characters are Platonic ideals standing in for a universal human. It doesn't matter who they are as long as they are us.

28 Weeks Later basically ignores everything that is expected of it, both as a film and as a genre film. In his review for the Guardian, Peter Bradshaw noted that "when people are infected [...] they turn instantly into slavering beasts, thus impatiently abolishing that dramatically invaluable interval, in which the infectee knows that there is no escape, and must either kill himself or beg others to do away with him." It's an accurate observation, but also another example of the film making a virtue of speed and subverting a perceived flaw. In 28 Weeks Later there is no time for rational thought or even an emotional response: the immediacy of transformation is overwhelming, and narrative drama is replaced by a visceral punch. The key transformation is that of Don. Within seconds he is transformed from a humiliated, redeemed man into a primal, bestial thing. Its violent immediacy is shocking and it has far greater impact than the overused scene that Bradshaw refers to.

It is also exquisitely shot. The original film was lauded for its use of London as a location; a startling, disquieting tableaux of abandoned streets. Re-watching 28 Days Later after this film, those scenes still retain an extraordinary visual potency, but Fresnadillo and Chediak manage to improve on the original. A city I have lived in for ten years is transformed into an alien necropolis where mundane infrastructure is rendered science fictional through framing and context. Andy and Tammy's scooter ride through this beautiful shell is at least the equal of Cillian Murphy's bedazzled stumble through a deserted Whitehall.

I mentioned Sunshine near the beginning of this review and the two films share similar strengths and weaknesses: both are visually impressive but pay scant regard to realism. I consider 28 Weeks Later a success rather than a failure because it embraces this fact, rather than equivocating in the manner of Sunshine. It is the sort of film that would carve 4 Real into its arm, and even if you think that is stupid you can't help but be impressed by the passion and bravado.

Martin Lewis lives in East London. His reviews have appeared in venues including Vector, SF Site, and The New York Review of SF.