In 2002, "28 Days Later..." opened in theaters with the promise: "Danny Boyle reinvents zombie horror". The talented Mr. Boyle ("Trainspotting") did little "reinventing", opting instead to make his creatures - who were not technically zombies - scream, vomit blood, bleed from the eyes and run really really fast. Sure we hadn't seen zombies do that before, but was that really a reinvention? It's not Mr. Boyle's fault that the "r-word" was already overused by the time his workmanlike, but ultimately unsatisfying, film hit theaters. And now, five years later, we have the amusingly titled "28 Weeks Later…". As it turns out, this sequel does even less reinventing than its predecessor, opting instead for more of the same, with decidedly mixed results.

A very promising opening finds Don (Robert Carlyle) and his wife Alice (Catherine McCormack) holed up in a small cottage somewhere outside London with a handful of other survivors. It quickly becomes clear that this scene takes place 28 weeks ago - during the first film. When the zombies attacks, in a moment of intensity which the rest of the film cannot hope to match, Don is forced to make a choice that - in a better film - would set up some very complex emotional pay-offs. Not so here. The film jumps ahead the titular 28 weeks, and finds Don a part of an "American-led NATO task force" set to "re-patriate" London. It seems the last infected victims of the "rage virus" have died out, the city has been secured and it's safe to move back - all under the watchful eye of some 1984-style surveillance.

It's not giving too much away to say that the virus returns and, again, the setup is promising. At that point, however, the film begins to fall apart. Suddenly, this high-security facility appears to be filled with more holes than the film's plot. It's odd that a script by four writers (Juan Carlos Fresnadillo, Rowan Joffe, Jesús Olmo and Enrique López Lavigne) could be so lazy, but apparently the virus is able to spread with an ease that goes from understandable to silly to unforgivable. Much of this is supposed to be explained by an "Access All Areas" pass, but that's far to flimsy to support the genocidal showdown that follows.

For a while, "28 Weeks" is on track to be the "Aliens" of this franchise, pitting a small group of survivors (led by Jeremy Renner's morally-minded soldier, Doyle) in an enclosed space against seemingly unstoppable multitudes. But as "28 Days" degenerated to an incongruous "Rambo-esque" climax, "28 Weeks" also squanders its premise and becomes a series of random, increasingly incomprehensible zombie attacks (sounds more like "Alien 3").

The most thankless role in the film (which is really saying something in a zombie movie) is a toss up between Idris Elba's overwhelmed commander Stone and Harold Perrineau's helicopter pilot Flynn. Mr. Perrineau's character, it seems, is able to spend as much time as he wants flying over London, plotting the secret extraction of his buddy Doyle, even as all his comrades are being overrun by zombie hoards. He does, however, have the pleasure of executing what is now, after "Grindhouse", the second zombie/helicopter face-off this season.

When "28 Days" came out it spawned a short resurgence of interest in the zombie genre (the new "Dawn of the Dead", "Land of the Dead") which was shot in the head before it could do much damage. "28 Weeks" attempts to reinvigorate the genre, but does precious little with it. The scenes of abandoned London streets - so striking in the first film - are here again and, since this is a sequel, there are many, many more. Mr. Fresnadillo, the film's director as well as co-writer, stages the goings-on with frenetic handheld camera that goes from stylish to "wait, who was that?" There also some hints of an Iraq allegory floating around, but with films like of "Children of Men", which have much more to say and say it better, "28 Weeks" feels like a long time ago.