Prosperous French lawyer Delphine (Sophie Colon) seemingly has it all. She’s married to Antoine (Matheo Capelli), an altruistic husband who adores their adopted children as much as she does. Proud of her “multinational” family, she spends her days sunbathing, swimming and enjoying cocktails with her children. While watching her husband and children laugh at a private joke, she receives a disturbing phone call, one that intimates that her husband is enjoying a romantic rendez-vous with one of her kids.

Initially, she seems nonplussed – she is, after all, a high profile lawyer who has received a number of scam calls. But then she starts to notice condoms piling in her daughter’s room, and her thoughts turn to the worse. Electing to keep a cool face – her son Aslan is moving to New York, after all – she carries on living in liberal suburbia before the truth comes out, and her life spirals out of control.

Like Jeanne Dielman, 23 quai du Commerce, 1080 Bruxelles (Chantal Akerman, 1975) before it, Endless Summer Syndrome details a woman’s nervous breakdown over the course of a weekend. By the time she gets to Sunday, Delphine has abandoned all pretence of happiness, and elects to confront her husband directly. It’s not like her to be passive aggressive: Not only does she tolerate her son’s marijuana habit, she also partakes in it from time to time. Antoine, by contrast, seems happier to spend his evenings reading Jack Kerouac, or playing scrabble. How could a man of his quiet nature do something so garish and destructive?

What’s most compelling about the film is its desire to break with social convention. The word “incest” is never uttered during the feature – director Kaveh Daneshmand opts to focus on the trauma that comes with infidelity. Delpine, unnaturally sylphlike and glamorous looking, is left wondering what emptiness lies in her husband’s life. When she hears the answer, it’s as aimless as the question she asked. But there’s no denying the pain Delphine suffers, which is evident from a solitary tear that falls down her face as she readies herself to re-enter the world at large.

With the exception of one more harrowing sex scene, imagined by Delphine in a moment of self-analysis, Endless Summer Syndrome is surprisingly tender in its depiction of nudity. Delphine herself happily takes her clothes off in the house she has bought with her own money, while the children (who seem closer than siblings normally are at this point of late adolescence) walk around the garden in various modes of undress. In one fiery scene, Delphine drags her daughter to the shower, peering for love bites, marks or clues that might insinuate her guilt.

Colon lets composer Matteo Hager takes on much of the heavy lifting (he uses dissonance whenever he performs keyboards), leaving her to stare vacantly into the void. You sense that a little bit of her soul is being chipped away by the depth of this family secret. Thus might explain why Delphine jumps into the pool with a violent sense of urgency. It’s here that the film’s central irony takes place: Keen to save herself from drowning, Delphine plunges headfirst into the only place she knows she’ll feel at peace; underwater.

Stylistically, Endless Summer Syndrome keeps it fairly simple, documenting the story in a solid, albeit admittedly static, manner. But what a story it is, exhibiting an alternative voice in these seemingly enlightened times. Colon commands the screen, but Capelli enjoys some meaty moments, especially in his depiction of a husband struck down by the severity of his actions. Make no mistake: Antoine loves his wife. But like so much in this life, love just isn’t enough.

Endless Summer Syndrome premiered at the First Feature Competition of the 27th Tallinn Black Nights Film Festival, when this piece was originally written. Its UK premiere takes place the 32nd edition of Raindance, which takes place between June 19th and 28th.