A lonely woman trudges the aisles of a cavernous warehouse, accompanied by the accusatory bleeps of the scanner that directs her every move. She picks objects off the shelves that serve other people’s needs – a baby doll, a vibrator, a rope washing line – as her own are slowly obliterated.

Laura Carreira’s acclaimed debut feature, On Falling, charts the exhausting and repetitive working week of an e-commerce employee. It is a testament to her skill as a director that she injects it with the pace, tension and jeopardy of a thriller.

“That vulnerability you experience when you have a precarious job, when you’re always on edge and there’s so little security – it has consequences,” says the Portuguese-born, Edinburgh-based film-maker. “We talk about the financial vulnerability, but very often we don’t think about what the cost is existentially.”

In On Falling, the migrant heroine Aurora, played by Portuguese actor Joana Santos, navigates the soul-destroying repercussions of the gig economy. With no cash to spend on activities that might invite human connection, she spends her spare time on her phone, scrolling through other, sunnier lives, a habit both self-harming and self-soothing. When disaster strikes and the phone is accidentally smashed, the £99 repair cost leaves her unable to pay the electricity bill in her cramped, shared digs and precipitates a shameful unravelling.

Carreira based her script on interviews with people working locally at what e-commerce companies such as Amazon would coyly describe as fulfilment centres. “They were expecting the job to be physically demanding, but didn’t realise how psychologically demanding it would be,” she says. “Then, when they get home, they are too tired to build a life outside work. After a few months of living that way, with few financial securities, people find the horizon a little darker.”

On Falling is produced by Ken Loach’s Sixteen Films, but Carreira brings intimacy and nuance to the often strident social-realist tradition. Her acute observations of the grinding infantilisation of the job are mostly taken from her interviews. When Aurora speedily meets her picking target, she is invited to choose a chocolate bar from a box on the desk of a manager who barely makes eye contact.

Meanwhile, she is chided for being disorganised when requesting a day off with insufficient notice, and the company’s struggling employees are encouraged to donate to an ecological charity that apparently matches corporate values. “Pickers I spoke to noticed these microaggressions with incredible accuracy,” Carreira says.

The honest portrayal of work on screen – what it pays, what it costs us and how we let it define us – is a longtime “obsession” for Carreira. As an 18-year-old, newly arrived in Edinburgh to study film and working to support herself, she didn’t recognise her contemporaries, who could head off on a road trip without bargaining their annual leave entitlement first.

Her early award-winning fiction shorts followed characters in similarly precarious jobs. “Films often avoid looking at work and I understand that, dramatically, it’s hard to film – especially work that tends to be repetitive. But to me, that was a challenge.” There’s one unedited shot in the film, she explains, that follows Aurora working in real time: “It feels long and I’m thinking, ‘That’s two minutes – this person is doing this 10 hours a day.’”

Carreira, who is 30, suggests that her generation is beginning to view work differently. “For us, it’s not the case that you work hard and get the rewards – half of us are living pay cheque to pay cheque. And when your free time is just spent preparing for the next working day, your experience becomes impoverished.”

But Carreira is adamant that On Falling should not simply prompt viewers to boycott e-commerce sites. Indeed, she makes plain in the film that some of the pickers are customers too: “They struggle to have time outside work to make the purchases they need. So it’s hard for the takeaway of the film to be a prescription on what you should do as a consumer. That’s another trap we can fall into – blaming what we’re going through on our consumer choices.”

The film doesn’t offer any clues to why this particular woman has ended up working in the warehouse. Carreira says she did this consciously: “We’re getting to know this character during one week and many, many different backgrounds could have led her to this position.”

It remains a mystery whether Aurora has supportive family back in Portugal who could help her, but we see that her shame becomes numbing as her meals dwindle to a stale cheese sandwich or a stolen packet of crisps. “Sometimes when you are struggling,” says Carreira, “you actually isolate yourself more, especially as a migrant, when there’s the expectation that you will build a better life.” But the absence of a tragic backstory is another challenge to the viewer – we can’t explain away Aurora’s poverty and isolation as consequent on some explicit circumstance. “It means we don’t have anyone to blame,” Carreira adds.

In earlier drafts of the script, Aurora encountered more conflict with her flatmates and co-workers, she says, but stripping it out made the story stronger and more realistic.

Carreira is too sophisticated a film-maker to bludgeon her audience into despair. Throughout the film are instances of vivid sweetness: a shared joke with a co-worker and a spark of romance across the canteen table; Aurora’s practical tenderness towards a drunken stranger; a no-strings inclusion in her gregarious – and comfortably self-employed – flatmate’s night out. At these moments Santos’s face is lit from within and we catch a glimpse of the big life Aurora is capable of living.

The film crew called these moments “the islands of care”, Carreira says. “Something I really believe in, and what I have encountered in life, is that people are kind and really want to care for each other. But the way we’re living isn’t providing enough opportunities to do that in a meaningful way. It’s these little moments that show our true intentions, and it’s easy to forget that and just blame each other for what we’re going through – when deep inside we’re there for each other. It would be good if we lived in an economic system that reflected that more regularly.”