Justine has never eaten meat, and Julia Ducournau’s Raw spends just enough time on that fact for us to feel what it costs her to lose it. Garance Marillier plays her as a first-year student at veterinary school, a stringent vegetarian dropped into a world the film presents as decadent, merciless and dangerously seductive. Released in 2017, it is filed under horror and drama. The second label does more work than the first.

The setup is simple. Justine wants to fit in, sets her principles aside and eats raw meat for the first time. The consequences are terrible, and she has no way of seeing them coming. It would be easy to read the meat as a stand-in for lost innocence, and the film invites that reading, but it never lets the hunger stay abstract. The appetite is physical, awkward and hard to hide from other people. Ducournau treats it as the first sign of a Justine who hasn’t introduced herself yet. The real drama is watching someone who thought she knew herself learn otherwise.

Marillier carries most of the film. She begins stiff and wary, like a person who has built a whole life out of a few firm refusals, and that stiffness gives way slowly. What I liked most is how seldom the performance explains itself. A less sure actress would have underlined every stage of the change. Marillier trusts us to notice it in the way she holds herself, in how long she looks at something, in how little she says when she wants it.

Ella Rumpf plays Alexia, Justine’s older sister, who is already at ease in the place that frightens her sibling. Rumpf gives her a careless confidence that is attractive and slightly menacing at once. The scenes between the two women are the liveliest in the film, because affection, rivalry and danger share the same room and none of them cancels the others out.

The school itself works as a machine for applying pressure. Hazing, parties and the constant demand to join in make refusing cost more than giving way. The initiation rituals are the obvious centre: grotesque, difficult to watch, and clear about what they are doing. They show how an institution turns coercion into custom and then calls it tradition. Ducournau has a sharp eye for the way groups dress cruelty up as fun, and the film is at its most unnerving when everyone else in the room seems to find the whole thing normal.

Raw has weaknesses. The middle stretch loses momentum. Some scenes land the same emotional blow twice, and the story seems to wait for the next shock instead of heading toward it. Several supporting characters stay thin. Adrien, played by Rabah Nait Oufella, and the father, played by Laurent Lucas, mostly exist to serve what happens to Justine and rarely become people in their own right. A film so fixed on one body and one appetite can afford some of that, though not all of it.

What Ducournau does well is hold a tone. Raw is funny in places, tender in others, and disturbing often enough that the laughter always arrives with a flinch attached. It treats female desire as confusing and frightening rather than as a code to be cracked, and it refuses to make Justine either a victim or a monster. She is both, and also neither.

The film premiered at Cannes in 2016, in the Critics’ Week sidebar rather than the main competition, and it has the feel of a first feature in the best sense: daring, rough in a few passages, and very sure of what it wants to show. I wish the last act had trusted its own ideas a little more. Still, it holds together because it never loses sight of its heroine. Few recent body-horror films look so convinced of their own appetite, and fewer still earn that confidence.