The evening before our interview, Stacie Passon was partying. She was in London to show her film, Concussion, at BFI Flare: London LGBT film festival, and took the opportunity to make a night of it. “I’ve had my fun,” she says the morning after, looking more impish than hungover at the offices of the film’s publicist. “Now I’m ready to go back to the children and the Volvo and the house.”

This is said with a knowing half-smile: the sentiment isn’t a million miles away from the tension at the heart of Concussion, a decidedly contemporary exploration of the competing urges for conventional domesticity and something a little more freaky. The story of Abby, a well-off lesbian housewife who takes a walk on the wild side after being smacked on the head with a baseball, it is Passon’s debut feature, and a notable success: since premiering at Sundance in January, it has won an award at Berlin and been picked up for distribution in 20-odd countries.

The smack on the head is merely a device to explore the discontents of middle age. And what’s immediately striking is that Abby’s frustrations are barely different from those of a straight woman in comparable circumstances. In the era of marriage equality, being a lesbian isn’t enough to disqualify you from the Madonna/whore dichotomy. “Politically, we searched for legitimacy for a long time,” says Passon, a Jewish New Jersey native full of wit, passion and occasional grandiosity. “We’ve put ourselves in this suburban existence, we’ve tried to change from within and, in the process, we’ve sort of lost what made us gay to begin with. We look around and we see straight couples having more fun that we are, essentially because they realised that this is a dead-end life if you don’t spice it up.”

Robin Weigert (Deadwood’s Calamity Jane) gives an ambivalent, sympathetic performance as Abby, a sometime interior decorator living outside New York City with her divorce-lawyer wife of two decades and their two sons. It seems to be an extremely comfortable suburban life of spin classes, yoga, home decoration and Little League – except that by the end of the opening credits, Abby is bleeding from the head. “Shut up, you little shit!” she barks at the son responsible for the poorly aimed throw. “I don’t want this …”

It becomes clear that “this” refers not only to a bashed noggin but to the settled routine Abby’s life has become. She is highly adept at the fine details of bourgeois living but increasingly alienated from them; she loves her wife but the passion has withered. Soon, almost inadvertently, Abby is dabbling in high-class sex work; an apartment in the city that she has bought to renovate and sell on doubles as a venue where she can entertain clients, who are described by the go-between who arranges the rendezvous as “young women with their father’s credit cards who like buying stuff”.

Over her encounters with a number of types, from shy students to assertive women her own age, Abby experiments with her own identity and desires, aiming to reach a new settlement with herself. It might sound like the stuff of cheesy softcore but the film is subtle, controlled and low on nudity – the trappings of decor are treated more fetishistically than women’s bodies – and Weigert’s performance anchors the action in psychological complexity.

The film’s promotional material bills Concussion as “a modern day twist on Belle de Jour“, Luis Buñuel’s 1967 tale of a housewife turned part-time prostitute, and numerous reviews have also made the connection. But as soon as I evoke the film as a model for her own, Passon wrinkles her nose. “Not at all,” she says, dismissing it as a “surrealist fantasy”. She was, she says, more inspired by Eve Ensler’s Vagina Monologues and the films of Chantal Akerman and Paul Mazursky. Oh, and her own experience.

“There are a lot of parallels to my life in this story,” says Passon. “It’s exactly the same.” Not that she’s been a sex worker, she clarifies. And not that she’s become alienated from her own wife (“I’m obligated to say that we have sex a lot and she’s an excellent lover and she’s fantastic in the sack. She’s very proud of me and [the film] has not caused any marital strain whatsoever.”) But Passon did spend two decades living with the same woman in the kind of well-heeled suburb where Abby resides, building a conventional career – in her case making commercial videos for clients including Donna Karan and Ralph Lauren – before turning 40 and feeling a lack.

“You start to see at a certain age what the rest of your life looks like and you’re desperate to do something to redress the balance,” she says. “I couldn’t be a lesbian hooker but I wanted to do something. This was my little red sports car.”

Not many people, of course, would be in a position to make a movie on a whim – and nor, in reality, was Passon. But she’s aware she had numerous advantages over most first-time film-makers, not least a wealth of professional contacts. These included producer Rose Troche, who directed the lesbian romance Go Fish in 1994 and recently oversaw The L Word on TV. “Rose taught me to get my head out of my ass,” Passon reports. “Originally I started the film with two and half minutes of Abby emptying the dishwasher and she saw the rough cut and said: ‘This might work against you …’ Rose is always fucking right.”

Director Stacie Passon. Photograph: David Levene for the Guardian

Moreover, privilege was the very subject Passon wanted to engage: her film exhibits an advertiser’s eye for luxurious production design and quietly gorgeous clothes yet finds absurdity in the power people can grant them over their lives. There is dialogue revolving around the crucial difference between parchment and beige as paint colours, and one of the most emotionally expressive moments relates to kitchen tiling. The gym is also a running theme.

“I see so much fixing up going on around me,” Passon says of her own life. “You saw it with the bodies in the film: they take [being in shape] to such an extreme, a lot of these women, because they don’t have a lot to do with their time. The whole idea of the film is with women advancing – with money, with more equality comes power and privilege. What kind of movie do you want to make with that privilege?”

Her response, she says, was “to stick a mirror in people’s faces and say: ‘This is what your power and your privilege look like’ … I’m basically giving everyone what they don’t want to see!” Much as she identifies with Abby’s situation, she doesn’t intend to indulge her. “She’s ridiculous! She’s fucking ridiculous! But that’s what’s happening … She realises that all of this is artifice and that she has to live her life the way she wants to live her life. All she can do is find herself as the subject of her life – that’s the only way she can be better for everyone around her and not be this miserable bitch that she is at the beginning.”

Of course, sexuality can’t be left out of the equation. By problematising the conventional model of a happy home and (without giving too much away) supporting its protagonist’s embrace of a more complex approach to sex, love and marriage, Concussion is about Abby coming to reject conformism as an aspiration. It could, I suggest, be described as a queer awakening. “Right,” Passon nods. “That’s actually really good. Yeah, she’s queer at the end. She is a bread-baking, gardening, doing-it-all-right, legitimate marriage, equality-loving, upstanding citizen at the beginning of this film. At the end she’s queer. Yay!”

Passon has a pet theory – “it’s so crackpot” – that there might be a genetic basis for the creativity and askance perspective often attributed to gay people throughout history. So, with regard to marriage, “it makes sense that you’d be in exactly the same place but that we’d see things differently.”

Or it might be that same-sex attraction has a genetic basis but the tendency to look at subjects from novel angles stems from queer people’s consciousness of their exclusion from the cultural mainstream. “Ah, very good!” Passon exclaims. “But I still yearn to be excluded! It’s so weird!” Maybe it’s just the recognition that some conditions of “normal” life are stifling for many people, whatever their sexuality, and non-straights do themselves a disservice by embracing them for the sake of conformity. This, Passon argues, is the basic moral of her tale. “It’s saying: ‘Come back to the fringe. Come back to what made you queer in the first place.’”

• Concussion is released in UK cinemas on 16 May