The movie is post-apocalyptic, and you should assume it's quite dark. This is the opening text provided to us (or at least this is the opening paragraph from the Wikipedia page summary, which I think is word-for-word from the film's title slide): "Humanity tried to prevent the impending ecological crisis by investing massively in genetic technology. It failed. Engineered viruses and organisms escaped into the wild. They wiped out edible plants, animals and large populations of humans. An oligarchy now thrives in enclosed cities called 'citadels,' while everyone else struggles to survive. For food, people rely on seeds traded by the citadels. However, these are coded to produce only one harvest."

Our main character is Vesper (Raffiella Chapman), who lives in a battered house in the forest with her paralyzed father (Richard Brake). He's kept alive by some weird bio-machinery that's never explained, and communicates with her through a floating drone / robot-head arrangement that speaks in his voice. Their nearest neighbour, with whom she has to deal occasionally, is Jonas (Eddie Marsan) - who is also Vesper's father's brother. It rapidly becomes clear why they don't live in Jonas' encampment, although there are quite a few people there: he's a vicious bastard who rules with an iron fist, and it's implied he's looking forward to "breeding" with Vesper.

Vesper finds Camellia (Rosy McEwen) in the forest, injured after her citadel flyer crashed. Vesper rescues her, although her father wants her to put Camellia back in the forest to fend for herself. Many lies are told, but eventually they form a bond. We find that Vesper is an extraordinary biologist, experimenting with plants in the hope of finding a way to better feed the people outside the citadels.

Vesper's life is grim and depressing. Much - in fact, I would say "most" - of what we see is never explained. It's visually interesting and internally consistent, but if you want to understand what's going on ... your hopes are likely to be dashed. In fact, the ending was ... hopeful, I think? Although it didn't look like Vesper's life was going to go well.

The end result was a product I have rather mixed feelings about. It's interesting to watch, it's very grim, and after you struggle through the grimness you're left on an ambiguous note that probably means more grimness. (It should be noted that since the COVID-19 pandemic I've had little stomach for depressing movies, so my judgment may be somewhat suspect.)