Regardless, it is always followed the western form of good guys, bad guys. Always. This one twists that from the very first moments which focuses on an appealing preadolescent girl in a hostile environment.
It helps to know as I did not that the disorder here is based on a real insect fungus.
The girl actress is fragile, grabbing all our native sympathetic pulls. Why this works is because of many shameful assumptions we carry: slight, submissive but sunny girl of color. A cooperating captive where the captive dynamics align with our strongest demons.
The Emma Atherton character as teacher is similar captive, unable to escape because of her emotional connection to what we know she thinks are the accidentally oppressed. The chemistry between these two is strong, evoking imagined backstories.
The sound/score is amazingly effective.
The surrounding chaos when attacked was well choreographed.
The twist at the end grabbed me viscerally. The trick isn't new of course, using a film to reinforce an identity the viewer grasps, then subverting that alliance. What made this is so effective is that the genre has such strong momentum, and that the identity we had pulled from us was so fundamental. It isn't our membership in a tribe that is stolen, but our excuse for living at all.
What did not work for me:
Amazingly, it was the Glen Close character. She has the job we find in uncinematic scifi films where she has to explain things. As a character, she seemed superfluous; so her role as explainer really is obvious and off-putting because she isn't in the story so much as between it and us.
The sets. Here's the thing. Its been ten years we assume since the pandemic. I know that the tendency is to show desolation visually, with extreme degradation, but the most effective scenes for me were those with ordinary environments and no ordinary motion.
The makeup. Someone decided to use the fungal notion but reference the old zombie tradition of rotting flesh. Can't have both.
The one joke: "I already had a cat." When you pull something like this, you acknowledge that there is a viewer to get the joke, and that you are invested in being playful with him/her. The character is taken out of the story and redefined as an entertainer for your pleasure. It breaks the story when it has the intent of this one.
The eating. If you decide to show a human fighting being devoured by beasts, then it should be as terrifying as the victim has it. This was almost a puppet show with carefully daubed chinblood shown afterward. I know it is a trope of the genre, like a Hong Kong martial arts fight where a single hit of a sword bloodlessly makes the bad guy fall dead instantly. But it works against the collective terror of the end.