Room faces a considerable challenge – how do you adapt a book that mostly takes place in a cramped room and is told from the perspective of a five-year-old boy?

Working from a screenplay by the source novel’s author Emma Donoghue, director Lenny Abrahamson (Frank) creates an entire world out of a single room and then expands that reality to bursting as its inhabitants face long overdue freedom. The odd premise is helped immeasurably by the small cast – led by Brie Larson as “Ma” and Vancouverite Jacob Tremblay as Jack – who commit whole-heartedly to this unique tale that’s less about enduring imprisonment and more about the indomitable human spirit.

Inspired by the horrific Fritzl case in Austria, Room details Ma and Jack’s plight locked in a small out-building that contains all the bare necessities to live but cruelly keeps them jailed. Their jailer (and Jack’s biological father) is Old Nick (Sean Bridgers, playing a role similar to his character from The Woman) – an initially shadowy figure that occasionally brings supplies and sleeps with Ma while Jack watches silently from a cupboard. It’s obviously a twisted situation, but the resilient Ma has built a fantasy world for her 5-year-old as a coping mechanism for them both and to shield the boy from their terrible situation.

To Jack, Room is his entire reality – everything outside those four walls is make believe. He watches TV but is told that those images are not real; he eats and sleeps and bathes, oblivious to the full breadth of life he’s missing. He and Ma make milk-snakes (from used egg shells), draw pictures, read books and pass the time. Cracks appear in the facade – like when a mouse gets in and Ma can’t explain the outside world and the animal’s origins. When Old Nick reveals he’s lost his job and isn’t sure how to support them, Ma makes the drastic decision to plot their escape by having Jack fake an illness so he can be smuggled out into the world.

There’s a heightened sense of fun and discovery and danger throughout, as Abrahamson often shoots from low angles to capture Jack’s point-of-view. Everyday items are given simplistic names without definitive articles, avatars that Jack gloms onto that form the fabric of his reality (he loves “Bed”, “Chair and “Wardrobe”). When it comes time to leave and Ma reveals that a whole world exists outside of Room, it’s bewildering and thrilling much as it would be to Jack. It also leads to the movie’s best scene, a nail-biting escape set to perfectly paired swelling music that’s stirringly triumphant.

The movie then (minor spoiler alert, although the trailer reveals the following and then some) turns to Ma and Jack’s re-integration into the outside world, and their journey towards a healthier relationship with each other. It’s an alternately heartbreaking and hopeful story, and one that wouldn’t have near the impact it does without the incredibly nuanced performances of the two leads.

Brie Larson has already proven to be a stunning young actress in movies like Short Term 12 and she continues her winning streak here. Jacob Tremblay astounds as well, a feat that’s doubly striking because of his young age (7-8 at the time of filming). It’s a welcome performance as much of the movie’s emotional beats rely on his authenticity, and it’d be a disaster without a strong performer at its centre.

And while that emotional honesty remains true for most of the film, it does stumble a bit in its latter half as the thrills of Ma and Jack’s escape fade away to be replaced by the mundanity (and difficulty) of everyday life. This could also be by design, although it doesn’t negate the feeling that the movie’s final third feels like falling action or an extended epilogue, though that’s a minor quibble for a movie that’s unusually upbeat about such dire circumstances.

Abrahamson has crafted a tale about the small and large ways in which we grow older and how those changes can affect our worldview, but through the eyes of a child who’s spent the first five years of his life in near-solitude and captivity. It’s a truly delicate feat and, much like Ma does with Jack, is accomplished through no small amount of care and feeling. An odd film that isn’t so much about crime and punishment (the fate of Old Nick is offhandedly revealed) but more about the wonder and amazement of the world as a child sees it. That child just happens to have grown up in truly unusual circumstances; he grew up in Room.

Room (2015)

Directed by Lenny Abrahamson

Runtime: 118 minutes