Like It Stains the Sands Red, which is out now, The Girl With All the Gifts is another example of how imagination and a good story can mine a seemingly exhausted well and still produce something fresh.

In this case that well is, once again, zombies, even though writer Mike Carey and director Colm McCarthy take their time revealing their zombie universe to you. In the beginning, all we know is that a young girl, Melanie (Sennia Nanua), is apparently one of a dozen or so children being held in a very high security prison.

She sleeps in her cell accompanied by some pictures cut out of a magazine, and when soldiers come to wake her up and she sweetly greets them with a chirpy 'good morning', they strap her wrists, legs and head into a specialised wheelchair, autmoatic weapons trained on her like she's a dangerous wild animal.

Along with her fellow inmates, Melanie is wheeled off to a chamber that turns out to be a classroom. Their teacher, Miss Justineau (Gemma Arterton) is unappreciated and dishevelled but appears to love her students, giving in to their pleas to give maths away for the day and read stories instead. After class, Melanie is wheeled back to her cell, unlocked carefully and closed in tight.

The reason for the heavy military presence and the apparent danger the kids present is because – as we learn slowly throughout the rest of the film – they're second generatoion 'hungries', the offspring of the first victims of a fungus that's spread workdwide, attacking the human brain and turning everyone into flesh eating undead.

Aside from Miss Justineau, Melanie also knows Dr Caldwell (Glenn Close), an eccentric scientist who visits her after hours with cruptic questions and who's working on a cure for the disease, and no-nonsense base commander Sergeant Parks (Paddy Considine), who appears to want nothing more than to put a bullet into the heads of every child they're holding captive.

Melanie is taken by Dr Caldwell to her lab one day instead of lessons and realises too late that she's the next in line to donate samples and tissue for the effort to find a cure – an operation she has to die for. But she's saved at the last second when the worst happens outside. The fences of the base fall and the zombie hordes break in, chaos reigning as soldiers, scientists and Melanie herself scramble to get away in the carnage.

She finds Miss Justineau and the pair fall in with Caldwell, Parks and two of his grunts, making good their escape in an armoured truck, Justineau insisting they take Melanie with them and revealing one of the first deep themes of The Girl With All The Gifts.

Even though the smell of flesh drives her mad with hunger and turns her into a hissing ghoul (which it does when the humans around her scrape off the special paste they slather over exposed skin to block their scent from her kind), Melanie can still talk, laugh and seemingly love. Is she a real child with an illness or a soulless monster, merely projecting the illusion of humanity and worthy of nothing but a bullet?

The small troop penetrates London on their quest for a base they think is still operating up north, finding a city swarming with hungries that they have to pick their way through like a minefield and introducing one of the film's coolest tweaks to traditional zombie lore. In this world, the hungries react only to sudden sound and movement, so by sneaking arm in arm through the crowds in absolute silence, the gang can go unnoticed, praying they don't accidentally tread on a stick or cough.

As they travel further from home, the film also shows us more of the state of the world and the apparent time it's been since the apocalypse. London is bombed out and overgrown, weeds and trees sprouting everywhere, a decades old layer of dust and decay across everything.

Meanwhile the clock is ticking in more ways than one. As Parks tries to get them to safety, Caldwell is still gunning for Melanie's samples, sure she's right on the cusp of a breakthrough. And with neither of them terribly concerned about the fate of a mere hungry, it's left up to Justineau to watch over Melanie.

But she also becomes an asset - because the other hungries aren't interested in her, Melanie can scout ahead to find the next place they can hole up on their journey, and she also gets to feed, removing the plastic, Hannibal Lecter-esque facemask her fellow travellers have put on to protect themselves from increasing hunger and gorging on the odd housecat running around the city or pigeon she catches on a rooftop.

But on their way to the base, two startling discoveries might transform not just the group's quest but the future of the world. One is a gang of hungry children who've either devolved from Melanie's state or advanced from that the of average hungry, forming the closest thing to a primitive society complete with leadership and customs the post apocalyptic world has seen.

The other is a huge chimney tower in the city where hungries have gone to die and where their bodies are spawning the next generation of the fungus – a vine that will transmit it by air and decisively wipe out the rest of humanity if the seed pods are unleashed.

The premise is great and adds something new to zombie lore, even if it feels like the script ran out of ideas about two thirds of the way through. It also has the curious quality of feeling like if it had stayed a bit avant garde and been as determined not to give up its secrets throughout like it was in the begining it would be a better experience, drawing you in more, making it more about what it doesn't show and forcing your imagination to work harder.

The subplot about the feral kids feels a little bit silly compared to the rest of the movie and the tone gets a bit too boisterous at that point, a bit too far removed from the air of quiet mystery the story's had until then.

But the visuals are good. The zombie make-up is effective and watching the group tiptoe through throngs of them is nerve-wracking. The scenes of a long-abandoned city also do a good job of conveying the passage of years even if the CGI to render them is a touch on the cheap side at times.

It's just that the imaginative and exciting start is kind of lost in favour of a more run of the mill zombie chase/end of the world threat thriller.