What at first appears to be a run-of-the-mill trauma drama about a family dealing with the eldest child’s anorexia nervosa gradually evolves into something odder and more original, even blackly comic, in Ungrateful Beings.

Working with a script half in English for the first time with a tale set partly in Croatia, Prague-based Slovene Olmo Omerzu seems to be playing here with a bigger budget and broader distribution ambitions than his mostly Czechia-centric earlier features, Family Film, Winter Flies and Bird Atlas. However, thematically and stylistically this is of a piece with its predecessors’ interest in dysfunctional families, troubled teens and tweens (once again directed with skill by Omerzu), and unexpected narrative diversions and surprises.

The unhappy family at the heart of the story this time consists of English dad David (played by Irish actor Barry Ward, arguably best known for Ken Loach’s Jimmy’s Hall and Netflix pic Maze), his wife Laura (Slovak actor Barbora Bobulova, Sacred Heart), and their two kids, 17-year-old Klara (Dexter Franc) and 13-year-old Theo (Antonin Chmela). We don’t actually get to meet Laura, apart from a glimpse on a cellphone, until a good way into the film because she and David are separated, mulling divorce.

As the film starts, David has taken the kids off to the Croatian coast for a camping vacation. While Theo, anxious about his parents’ split, strives to make himself agreeable to his dad, Klara seems to be in training for nationals as a champion sulker, resistant to every attempt to have fun. More troubling, she refuses to eat more than a few mouthfuls of food a day, and it becomes apparent that medical intervention has already been tried. But nothing David makes for dinner or tries to say seems enough to compel her to eat, let alone ameliorate her depressive state and anorexic behavior. (The frequent moments where she measures parts of her body with her hands, or checks herself with selfies, look cribbed straight out of a handbook on warning signs parents should look out for.)

And then suddenly, with the swift, irrational passion only teenagers are capable of, Klara falls in love with slightly older local Denis (Timon Sturbej), a cheeky blond Adonis with the kind of chip on his shoulder that makes him pure catnip to teen kittens. Born out of matrimony to a now-dead mother and a local burgher he doesn’t get on with, Denis makes his living catching fish to sell to the local restaurants and maybe hustling the tourists. David’s first instinct is to keep him well away from Klara, except that for the first time in ages she starts eating at Denis’ behest and that outweighs anything in the debit column.

Omerzu and his team aren’t above deploying romantic backlighting for midnight kisses and some of the clichés of young-love cinema, but thankfully that’s only to subvert them as the film goes on. Let’s just say the script by Omerzu, regular collaborator Nebojsa Pop-Tasic and Kasha Jandackova zags and zigs in interesting directions, starting with the unexpected death of Denis’ father, which disrupts the lovers’ romantic idyll.

Suspicions fall on Denis, and David soon throws the kids in the car and heads back home to face Laura, furious at first to hear about Klara’s sexual awakening even as she begrudgingly admits that getting the girl to eat was the top priority. When Klara ends up in the local hospital’s anorexic ward, David and Laura must resort to even more desperate measures, which paradoxically help thaw out their own emotional cold war.

In other hands, this material could easily seem absurd, especially the extremes Omerzu is willing to go to in the last act. And yet the command of tone is confident enough and the cast sufficiently adept that it’s easy to be seduced by the film’s sly fan dance of revelation and concealment. As drawn here, the characters are an entirely plausible, fallible mix of peevishness, self-interest and self-sacrifice, especially the parents who learn the most about themselves and each other when push finally comes to shove. Still, Omerzu’s touch is light, ironic and gently amused, a little reminiscent of François Ozon, who has a similar facility with twisty sly comedy-drama grounded in pain.