Following a deadly fungal outbreak, survivors live in secure military bases while the infected roam outside as mindless, flesh-eating 'hungries'. But children born to hungries are different - they can think. While treated like dangerous animals, symptomatic youngsters like Melanie (newcomer Sennia Nanua) are key to any cure. So when the base is breached, Melanie finds herself accompanying her kindly teacher Helen (Gemma Arterton), chief scientist Caldwell (Glenn Close) and skeptical soldier Parks (Paddy Considine) on the ultimate survival mission. Adapted by Mike Carey from his acclaimed novel and intriguingly orchestrated by Peaky Blinders director Colm McCarthy, this is as eerie, intelligent and grimly engrossing as the zombie apocalypse gets.
While resolutely following in the gammy footsteps of 28 Days Later and The Walking Dead, writer Mike Carey's version of zombageddon has plenty of its own ideas to chew on.
The intrigue begins with a seemingly ordinary girl, Melanie (Nanua), being roused from her jail cell by twitchy soldiers, shackled to a wheelchair, and delivered to a makeshift classroom with a group of similarly restrained youngsters.
Only their teacher Miss Justineau (Arterton) treats them like children. We soon find out why. After a symbolic lesson about the myth of Pandora, the Greek maiden who held the key to all humanity's ills, in comes hard-nosed Sergeant Parks (Considine) to give a rather less subtle demonstration of their true nature.
They are, in fact, the offspring of 'hungries', victims of a fungal plague that kills the mind but keeps the body running - given a regular supply of fresh meat.
However, head clinician and keen vivisectionist Dr Caldwell (Close) believes that since second-generation hungries have all their mental faculties, their brains can literally be picked to create a vaccine.
Alas, her work is interrupted when the base is stormed by the ravening hordes. Amidst scenes of splendidly orchestrated chaos, she is lucky enough to escape with Parks, Melanie and Miss Justineau. And a couple of grunts.
From there, the narrative enters more traditional zombie territory as the mutually suspicious group heads for Britain's main survivor facility, 'The Beacon'.
They get waylaid in a gone-to-seed London where feral children run wild and the zombified masses loiter around shopping malls in a catatonic state, as if unsure what to do now that Primark has closed and Greggs have run out of pasties. No change there, then.
All joking aside, director McCarthy and his perform wonders on a small budget, literally turning London into an urban jungle and cheekily transforming the BT Tower into a giant myco-transmitter.
Alas, while raising interesting ethical points about the greater good and self-preservation, there are some distracting spots of rot in its logic. Why do the hungries react so differently (to loud noises, for instance) when they're portrayed as having a pack instinct? And how does a yappy dog survive on its own for so long?
One or two scenes also probably looked better on paper than in the final cut, particularly when Melanie goes to bat for her companions. And the ending. The intention is clear, but the effect isn't hugely convincing.
For the most part, though, this is a superior addition to the genre that offers much food for thought.
Oh, and that zombie fungus they're talking about? It exists.