It’s hard to think of a movie adaptation of a book that feels truer and more loyal to its source than Room. In part, that’s thanks to the precise environment Emma Donoghue crafted in her Orange Prize-winning 2010 novel, the majority of which was set in an 11-foot by 11-foot insulated space with a lone skylight. But the book was also narrated in its entirety by a 5-year-old boy, and much of its power and poignancy came from how well Donoghue captured the voice and perspective of such a small child—a much trickier endeavor for film, where childlike naivete and wonder can often become mawkish.

Room’s director, Lenny Abrahamson—whose previous film was the offbeat Frank, starring Michael Fassbender as an eccentric musician who wears a large papier-maché head—navigates the balance with remarkable finesse, working from a screenplay written by Donoghue. The movie opens with Jack (Jacob Tremblay) describing the events of his fifth birthday, and the details of the tiny universe he inhabits, Room. His Ma (Brie Larson), he explains, was alone in Room until he “zoomed down from heaven” to save her.

The agony of Donoghue’s book is in how long it takes to piece together the evidence given Jack’s limited capabilities as an interpreter, but here it’s soon clear that Ma and Jack are prisoners. Their only visitor is Old Nick (Sean Bridgers), who’s keeping them captive, and who rapes Ma while Jack sleeps in the closet.

When Old Nick reveals that he’s lost his job, and might also lose his house, Ma, realizing he will probably kill them both rather than let them escape, begins hatching a plan to set Jack free. In the space of a few days, she tries to teach Jack everything about the outside world—often a logical and philosophical conundrum as much as a practical one, since all he can see of it is empty sky. Room is unmistakably an allegory for the painful process of growing up, and here it’s rendered in rapid time, with Jack stubbornly resisting the puzzling, threatening barrage of new information, and Ma forced to move past his discomfort. Abrahamson suffuses these scenes with fierce suspense, adding urgency to Ma’s lessons in how to understand the world.

Perhaps it’s natural that an adult audience would see the events unfolding much more from Ma’s point of view than Jack’s, but it’s also a testament to Larson’s performance. She’s restrained but tightly coiled, practical and maternal, but also unpredictable. The world that Ma and Jack live in is one that Ma has made to protect and nourish her child as best she can—they exercise in the small space, read, and watch TV only for an hour a day, so it doesn’t “rot our brains,” as Jack explains. With Jack deprived of any social contact, every single item in Room becomes his friend: Wardrobe, Bed, Toilet, Lamp, Egg Snake (which they craft from leftover eggshells and hide under the bed). Tremblay is equally extraordinary in his role, imbuing tiny Jack with natural amounts of charm, courage, wit, and fear.

It’s hard to imagine that such a bleak scenario could be made so beautiful, but Abrahamson finds poetry in the small details of Room, captured through grey filters to emphasize the lack of light. More, though, the film captivates because of its central duo, who are each other’s whole world. As much as the audience empathizes with Jack, and feels his agony at losing what he interprets as a safe and familiar environment, so too they feel Ma’s pain in having to disrupt it.

Room is the kind of drama that feels tailor-made for theater, with its limited locales and emotional intensity. But it’s after Jack finally leaves the space for the first time that the potency of film is most felt—in its ability to express his wonder and confusion and discombobulation at seeing things he’d only experienced through a screen. It’s to Room’s credit that it makes that disorientation so visceral to viewers, communicating the angst and the elation of breaking free.