Norwegian writer-director Camilla Strøm Henriksen admits that she appreciates “things that are not too much in your face”. For her understated but visceral debut Phoenix, she brings her own experience about growing up too early among inept artistic parents to the cinema with unsentimental skill. Screened during the Glasgow Youth Film Festival along with a live Q&A with Henriksen and lead actress Ylva Bjørkaas Thedin in her first role, this was definitely one of the highlights of the festival. Responding to a moved audience with humility and passion, the pair rounded off the intimate experience of the film with a spark that remained palpable on your way home through moody Glasgow.

Introverted teenager Jill (a subdued but emotionally loaded performance by Thedin) lives with her younger brother Bo (Casper Falck-Løvås) and her labile mother Astrid (Maria Bonnevie) in a small Oslo flat. Astrid spends most of her time smoking in bed, unable to break through as an artist with her earthy mixed-media work and find a permanent job to secure an income. Trying to act as a substitute head of the family, Jill has little opportunity to indulge in the trials and tribulations of teenage life. As an unexpected job interview for Astrid conflicts with Jill’s 14th birthday and a visit from her alienated jazz musician dad, tensions and expectations come to a head until a tragic event tests Jill’s fragile capacity to act like an adult one more time.

What could’ve been a stifling melodrama in somebody else’s hands blossoms into a maturely handled chamber piece under Henriksen’s direction – her translation from personal experience into screenplay is self-conscious and palpable through small gestures, looks and body language of the actors. Maria Bonnevie gives a striking performance as the beautiful but brittle mother, her eyes agog with anticipated disaster. With her flowering robes and unmade-up face, she reminds a lot of Michelle Pfeiffer’s portrayal of a similar character in the often overlooked White Oleander. As the story progresses, Jill’s experience of her family’s rotting integrity becomes carefully infused with cinematic horror elements: when she descends to the basement to look for her mother or goes through the apartment at night, the framing, sound and underlit cinematography bear spooky resemblance to the way suspicion is played with in indie horrors like It Follows or Teeth. Jill’s grown-up façade starts wearing down when her imagination takes over and she keeps seeing a bug-shaped, outsized creature slithering around the flat that nobody else can see – or so she thinks. But there is no sensationalism or desire to shock in these scenes – rather, Henriksen carefully hints at the horror underlying everyday experiences. Jill’s need to think like a child is palpable we see her having a Cinderella moment: wearing a dazzling pink sequin gown she receives as a birthday present, she has a short-lived taste of ‘the good life’ when her father takes the siblings to a posh hotel to eat chocolates, an even posher restaurant and his own gig.

The sound design of Phoenix is an absolute delight: during the Q&A, Henriksen explained that it was important to her that the flat was never quiet. Considerately placed, minute sounds like the slicing of bread, the clinking of a porcelain cup or hushed voices behind half-closed doors are amplified, become emotionally charged and extend the idea of the flat as a living body. Colour and lighting code the flow of narrative delicately, from the rustic browns and cave-like shadows of Astrid’s world to the bright, clinically white hotel luxury associated with the deceptively serene father.

Henriksen does her best to resist romanticisation in this Fish Tank-meets-Thelma experience, but can’t always avoid occasional relapses: the grandeur of the heavily violin-led soundtrack somewhat awkwardly clashes with the film’s low-key agenda while some moments in the narrative (e.g. Jill daydreaming about standing on stage with her father playing the trumpet in slow-mo) appear insecure and overbaked. But these flaws are quickly beaten by the film’s passion to provide a sincere portrayal of an underrepresented family situation that somehow achieves to be discreet and bold at the same time.

Glasgow Youth Film Festival is programmed annually by 15-19 year-olds. Phoenix screens at GFT 23-26 September.