A square of blue sky no bigger than two sheets of A4 paper, lodged in a six-foot by eight-foot concrete- enforced garden shed - this is the unlikely starting point for imagination in director Lenny Abrahamson's new movie, Room.

Opening in Singapore tomorrow, the 118-minute feature film is based on Emma Donoghue's book of the same name. Fast gaining Oscar talk across the festival circuit, it had faced hurdles most Hollywood directors would prefer to sidestep, by subject if not technique.

"The challenges are in very distinct parts. Half of the film takes place in a very small space. You're also working with a child," Abrahamson says in an interview with The Straits Times.

But the Irishman is also the fabled auteur of last year's Frank, which saw lead actor Michael Fassbender spend 99 per cent of his screen time faceless, inside a papier-mache mask while recreating the eccentric life of the musician Frank Sidebottom.

"It's a combination of all those things, really. I suppose I'm drawn to these challenges," Abrahamson adds.

He makes a third point about the defiance of the movie's cryptic, single-word title, camouflaging its layered and dark subject matter told through a beguiled five- year-old's perspective: An unbearably young mother appears to have been imprisoned for years together with her son by her rapist. In between making too-skinny sandwiches, eggshell garlands, chasing away mice and doing daily sit-ups, she schemes a dangerous escape.

But what happens afterwards… if she escapes? Will she escape?

Yet "it's not a film about incarceration, it's a film about love," Abrahamson contests. (Potential spoilers ahead.)

"It's a big choice with the distributors about whether they reveal the escape. But, as far as I see it, you can't," he adds.

"There's no way of expanding the subject to deal with what the film really is about. A huge number of people who would love the film would otherwise not go to see it."

Indeed, "magical childhood skit turned suspense thriller turned trauma-drama turned life-affirming tearjerker" appears be the clunky portmanteau genre for this difficult-to-pin-down outing, starring relative newcomers Brie Larson (Short Term 12, 2013) and Jacob Tremblay. And yet, Abrahamson is unperturbed.

"Because American television has gotten so much better, you don't always have to underestimate your audiences now," he says.

"There's a whole openness to a subtler type of stories today. I think people are pleased that Room is affecting audiences even though it's a film that does not cater to everyone in a direct, broad way."

There are, initially, poetic tributes to childhood. The 49-year-old director first read Donoghue's novel in 2011, when his children, a son and a daughter, were young.

"My boy was not a million miles from Jack's character - you know, that age. I had been thinking so much about kids. Becoming a father, becoming a father in my early 40s, and then having a child in your life makes you think about your childhood.

"When I read the novel, I thought this was a brilliant way of exploring universal ideas of childhood and parenting, and being parented."

Paradoxically, it is the constricted space within the four walls of the garden shed prison that provides the safety and security for a mother and child's imagination to spring into growth.

"There's something dangerous about this place but, at the same time, the dangers are clear. There is a forest around the cottage but the cottage is warm; the fears are of the outside. Childhood personifies these fears as monsters, but what kids are afraid of is the unknown."

Adulthood, however, is the real world, where "nothing means what it seems to mean and people's reactions and motivations are unclear", the film-maker continues.

"Adulthood is when you realise, you lose… there is no magic safe place, you can't pull your sheets above your head and pretend that nothing can hurt you."

Adulthood, not surprisingly, then, is when mother and child flee their prison only to find that the world outside, years away from their love-filled space of enforced solitary confinement, is a place of incomprehensible love-filled hurts.

Yes, there are power showers, wall-to-wall carpets and outdoor playgrounds. But there are also relatives who become anxious, unaccepting alcoholic strangers.

"You spend the first half of the film desperately hoping that they will get out, the mother sees it as the complete solution to her terrible problem," Abrahamson explains.

"But then, they get out and you see her feeling as she is, and he asks, 'How long will we be here?' And she says, 'You live here now.' I wanted the audience to similarly feel that turn, that journey."

Telling this story on the silver screen with all the obvious challenges was helped by shooting chronologically, which meant seven months of prep work and long periods of filming.

"For the little boy, it's so much easier to help him understand. I also wanted to have these little echoes of the first half of the film in the second half. It's very hard to do that without having done the first half," Abrahamson says.

To keep things real, he insisted on a strict sans make-up regime. Lead actress Larsen also spent several weeks on the set hanging out with child actor Tremblay, "playing Lego together, making things that you see in the flat in the movie together, in the flat".

"One thing we decided was whoever plays Ma must be warm and have a great sense of humour," Abrahamson adds.

"Because if this were to work at all, she would have to form a relationship with a little boy. Some actors - they would have to be un-talked to, they need to be in their zone, they go straight back to the trailer after a shoot.

"But Brie wasn't like that. By day three, Brie and Jake were jumping up and down on the beds. They bonded. It was something special."

Indeed, one suspects the sheer spirituality of the film is found in the uncomplicated joy of working with children. The team admits that the many dark themes - of kidnapping, sexual assault, imprisonment, depression and suicide - were never made clear to the seven-year- old Tremblay.

For a film based primarily on a child's perspective, the naturalness and honesty wrought about through this little white lie made all the difference to the eventual storytelling.

"Listen, kids understand the idea of bad people - how many fairy stories are about being locked up? Fairy tales have this huge sexual dimension to them, kids just don't recognise that… yet," Abrahamson muses with a raconteur's smile.

"Jake would be perfectly happy to go with the idea that this was a story about a nasty guy who's locked them up and I think as a seven-year-old, he would have intimations that there's something…

"But you know what?" he adds with a conspirational wink.

"I think he's not going to go there until he's ready to."

• Room opens in Singapore tomorrow.