If the notion of another cornball, family-themed festive movie fills you with deepest dread, then this new romantic comedy – starring Kristen Stewart and Mackenzie Davis as a couple enduring a conservative holiday gathering – sprinkles some sweetly subversive fairy dust over the old seasonal formulas.

Davis is Harper, a Pittsburgh political journalist who’s decided to bring the love of her life – Stewart’s graduate art historian Abby – to her upper-middle-class parents’ annual Christmas gathering. Abby, who lost her parents as a teenager and isn’t too big on the season’s ritual, is nonetheless thrilled – she plans to pop the question and ask for dad’s permission to get engaged.

There’s just one hitch: Harper hasn’t come out to her family. So Abby is forced to pose as her roommate, with both pretending to be straight, to complete the ruse.

“It’s five days,” says Abby, “how bad can it be?”

Though the premise seems primed for some Meet the Parents-style hilarity, actor-turned-director Clea DuVall, who co-wrote the screenplay with Mary Holland, takes a gentler, more emotionally nuanced approach to the impending carousel of charades.

Abby’s best friend John is played by Schitt’s Creek‘s wonderfully haughty Dan Levy. Photo: Sony Pictures/Lacey Terrell

She sets her film up with the festive vanilla glow of a Hallmark Christmas movie, bathing everything in warm amber hues (DP John Guleserian also shot the catalogue-perfect Love, Simon), with cheesy greeting card title cards, Phil Spector-sound-a-like songs (courtesy of Sia), and a quaint local cinema playing – what else – It’s a Wonderful Life.

It’s a checklist of everything the conventionally straight Christmas movie has come to embody, a cheeky declaration of holiday classic intent.

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The couple’s tender rapport is introduced with a similar minimum of fuss: the statuesque Davis and the slouchy, tactile Stewart are a good match, sharing the ease and lived-in chemistry of a real couple.

When Abby and Harper arrive at the stately Pennsylvania home of the latter’s parents, it’s refreshing to see the family is less a moneyed caricature than a keenly sketched comic portrait of a loving, if frayed family holding it together for the holidays.

Actor-turned-director Clea DuVall (But I’m a Cheerleader) came out to her own mum at Christmas, in the heat of an argument. Photo: Sony Pictures/Lacey Terrell

Patriarch Ted (Victor Garber) is a conservative city councilman running for mayor, and he and his pinched, punctilious wife, Tipper (Mary Steenburgen) are busy keeping up appearances to secure campaign donors at various country club fundraisers. (Wearing a fabulous helmet of hair and taking fussy family snaps on her iPad, Steenburgen is a gift.)

Also in attendance are Harper’s sisters Jane (co-writer Holland), a slightly annoying, aspiring fantasy novel writer; Sloane (Alison Brie), a designer of bespoke gift baskets, who boasts of being on Gwyneth Paltrow’s Goop radar; Sloane’s husband Eric (Burl Moseley) and their amusingly surly kids (Anis and Asiyih N’Dobe) – who the campaigning Ted keeps on hand for expedient photo ops, like some festive version of Get Out.

It’s a stacked ensemble that suggests a lively, long-standing sibling rivalry, while DuVall’s visual shorthand fills out the details – like the teen magazine pin-up of Josh Hartnett that remains in Harper’s old room, a reminder of a distant, failed straight phase that suddenly seems, now that she’s back in the family home, to take on the immediacy of the present.

DuVall told Variety that after meeting Stewart she “couldn’t imagine making the movie with anybody else”. Photo: Sony Pictures/Lacey Terrell

Meanwhile, Abby’s best friend John, played by Schitt’s Creek‘s wonderfully haughty Dan Levy, is on call to offer relationship advice; with a generous wink, the gay best friend is the one rom-com trope DuVall seems only too happy to play up.

For a while, at least, the extended family seems to buy the line that Abby and Harper are platonic roommates (“Have they ever met a lesbian?” John wonders incredulously), and the game of deception makes for some serviceable farce – including one dependable scene in which, yes, Abby is literally trapped in a closet.

But Abby’s increasingly suffocating pretence begins to unravel with the appearance of Riley (Aubrey Plaza), Harper’s first girlfriend.

Riley’s cruel outing at a formative age has left her ostracised as the local lesbian among her stuffy milieu, though she’s found community in the town’s small gaybourhood, where she consoles fellow outsider Abby.

Their burgeoning friendship, forged in the shadows, is enough to make one hope for a spin-off movie about their adventures around town – Plaza and Stewart’s duelling blazer game would be worth the ticket alone.

Levy’s energy is “inspires fellow actors”, according to Stewart Photo: Sony Pictures

Stewart, in particular – who mopes and simmers as only she knows how – brings a dramatic weight to the film that goes beyond its broader outline.

This is the second feature for queer filmmaker DuVall, a veteran actor whose credits stretch across three decades but is perhaps most fondly remembered – at least by certain audiences – as Natasha Lyonne’s romantic partner in Jamie Babbitt’s But I’m a Cheerleader (1999), a key title in the teen coming out canon. (The two actors reunited as lovers for DuVall’s 2016 debut, The Intervention.)

“I wanted to be proud of the couple. I wanted to be like, ‘I like these people’,” Stewart says. Photo: Sony Pictures/Lacey Terrell

DuVall has a sure hand with performance. She sustains the plot’s various amusements, but her instincts aren’t always for the big, easy laugh. That things will come to a head, with Christmas trees toppled and family grievances aired, is a given, but the comic set-pieces tend to underwhelm next to the film’s more attentive dramatic shading.

It’s a tricky tone to navigate, but DuVall and her cast manage to tease the emotion out of the genre’s cliches.

If the movie’s resolution seems a bit easy, then it’s one couched in hope and acceptance – and the idea that a queer audience deserves a seasonal fantasy every bit as fireplace-warm as the regularly-scheduled holiday fare. In a long and conventional tradition of Christmas films, Happiest Season is a quietly subversive pleasure.

Happiest Season is in cinemas now.

-ABC