This 2016 movie is based on the 2014 novel, which in turn was inspired by a short story.
Melanie (played by Sennia Nanua) is the brightest among her classmates in a prison-like existence somewhere in the U.K. The children are supervised by Sergeant Parkes (Paddy Considine) and his soldiers, as if they were dangerous animals. Their favorite teacher is Miss Justineau (played by Gemma Arterton). In charge of everyone is sinister Dr. Caldwell (played by Glenn Close).
Dr. Caldwell has Melanie brought to the lab and is about to remove her brain and spine, when the military base is abruptly assaulted by 'hungries' (zombies). Escaping in a military vehicle are six people: Sergeant Parkes, soldier Gallagher (played by Fisayo Akinade), another soldier who doesn't survive their next encounter, Miss Justineau, Melanie, and Dr. Caldwell.
Unable to contact anyone by radio, the group decides to go south through London to Beacon, the last safe city. It is now revealed that Melanie (and the other 'children') are infected with the same fungus that causes adults to turn into hungries. Dr. Caldwell promises that if she can get proper medical equipment, she can finally make a vaccine to save humanity (at the cost of Melanie's life).
The rest of the movie is a combination of survival and discovery, as the group drives and hikes through a landscape abandoned a decade ago when the zombie plague began.
The hungries are in a dormant state until triggered by the smell of prey, loud noise, or sudden motion. Once activated, they are fast but not clever.
The movie has a few twists along the way, major characters die, and Melanie is faced with a difficult decision. The ending is both 'happy' and horrific.
How does the movie compare to the novel? The movie tracks fairly well with the novel, except condensed. For example, the entire 'Junkers' subplot is gone. The children in the novel were described as cold, pale and repellent; that's missing in the movie. In the novel, Dr. Caldwell is dissecting the children in a desperate move to understand the plague, and learns key information during the journey; in the movie, she already knows everything, and just wants to save humanity with the vaccine. That makes her less pathologically evil than she was in the novel! In the novel, the zombie plague started several decades ago; in the movie, only one decade ago.
Some changes are due to budget and vision. The grenade fight from the novel is gone. The giant double-wide, mobile, tracked research station has turned into a truck with connecting trailers. The massive fungal dome over south London has become a Jack-in-the-Beanstalk-type vertical growth. Most sexual content, porn references, and nudity from the novel have been removed. There's a slightly different explanation for where the children come from, the final scenes are simplified, and the fate of the children left on the base is resolved.
Some minor problems occur due to the changes from the novel to the movie. The loss of the Junkers subplot messes up the scene where Melanie rescues Miss Justineau – in the novel, she saves her from Junkers; in the movie, she saves her from soldiers who inexplicably decide to execute the teacher while surrounded by attacking hungries! The scene with the hungry pushing a stroller was key information in the novel, but irrelevant (though creepy) in the movie. In the novel, Melanie captures a fox to use to distract the hungries; in the movie, she finds a dog in a home (it survived for a decade?).
Having read the novel, I had trouble liking the movie at first. There wasn't time to develop the relationships, and most of the major characters were 'warmer' than in the novel. It was confusing at first to discover Melanie was now black instead of deathly pale white as in the novel, while Miss Justineau went from dark brown to white. Gemma Arterton as Miss Justineau had disappointingly little chemistry with the children. Paddy Considine was fine as a nicer version of Sergeant. Glenn Close was mostly fine as the 'nicer' Dr. Caldwell, but over-acted a few times. The key for this plot is making the viewer believe that Melanie is actually dangerous. In the novel, that was apparent from the start; in the movie, Melanie starts as a 'cute little moppet' and only late in the movie do we see the full reveal. By the end of the movie, I was quite impressed with Sennia Nanua's performance as Melanie.
Note that, although this movie is about a ten-year-old zombie girl, there's enough zombie-type violence that you probably wouldn't want your little children to watch this.
Can you game it? Easily. There's basically two scenario types here: defend against zombie assault, or sneak past dormant zombies/fight if they wake up.
Fun facts: Some of the movie was shot near Chernobyl. Zombie extras included the author and a relative of Glenn Close.
I enjoyed the movie. Not your usual zombie movie. Recommended.