Have yourself a merry little Christmas as Happiest Season sets out to make the Yuletide gay.

More of a holiday dramedy than a jolly seasonal RomCom, director Clea DuVall’s loosely autobiographical “Happiest Season” seeks to invert the traditional Christmas movie tropes but inadvertently finds itself trapped by the conventions of the genre and a too glib approach to seasonal redemption.

Abby (Kristen Stewart) and Harper (McKenzie Davis) have been dating for a year and are madly in love. One night, carried away by the festive atmosphere of the snowy, fairy light-strewn streets, Harper impetuously invites Abby to celebrate the holidays with her at her family home. Abby secretly decides this is the perfect opportunity to meet Harper’s parents and propose to her on Christmas morning. On their way to Harper’s family home, though, Harper confesses that she has not come out to her parents and fears it will compromise her father’s bid to become the Mayor campaign for mayor. In order to keep up the pretence, she asks Abby to pretend to be her straight roommate for the holidays and promises she will tell her parents after Christmas.

In concept, “Happiest Season” is a very familiar set-up and you could, with very little amendment, replace the same-sex ‘secret’ with any other factor and tell the same kind of story. In execution, it’s archly unfamiliar – and often unpleasant – thanks to the characters we’re asked to embrace and, ultimately, forgive.

There’s nothing new in the idea of bringing home a new partner for the appraisal by judgemental and ambitious parents but the difference here is that Harpers family are genuinely horrible. Her mother (Mary Steenburgen), in addition to being cold, judgemental and snobby is also incredibly rude and lacking in the social graces. Likewise, her father is fully disengaged with anything apart from his own ambitions and her sisters are a tag team of frosty bitchiness and goofy hyperactivity, all of which might have been endurable were it not for the fact that as the movie progresses, you soon realise that Harper is every bit as awful as her misanthropic family.

They say you should always leave the audience wanting more, but when the audience’s want is for more of your supporting characters instead of your leads, something’s gone a bit wrong. McKenzie Davis struggles to engender any empathy as Harper continually lies, gaslights or simply ignores Abby while her family’s hostility and rudeness just keeps on going.

Thankfully there’s solace for Abby (and the audience) in Aubrey Plaza’s Riley and Dan Levy’s John who, together with Kristen Stewart, form a wholesome trinity upon whom the film should have pivoted to focus, perhaps teaching Harper a harsher but more salient lesson by losing Abby to another of her mistreated and discarded exes.

Adding injury to the various insults, though, is an entirely unconvincing and unearned Damascene conversion and redemption of every single unlikable character when McKenzie is forced to come out to her parents and family. They talk the talk when they’re faced with no choice but given they’ve failed to walk the walk for decades prior to this, it’s a saccharine ending which feels sickly rather than sweet.  

It’s great to see a diverse and inclusive take on the classic Christmas tropes and it’s worth seeing just for the charm and screen chemistry of Stewart, Plaza and Levy but “Happiest Season” isn’t some barrier-shattering redefinition of holiday cheer; at most it’s – to paraphrase Ari Aster – elevated Hallmark.