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arrowing yet hopeful, Room is a story that will linger in your mind long after it has finished. It centers on the weight of parent-child dependency in any situation '€” even the most horrible.

Based on a 2010 novel by Emma Donoghue (who was inspired by the horrendous case of Joseph Fritzl and who also wrote the screenplay), Room tells of a young mother and her 5-year-old son who are kept as captives inside a locked room by a man they dub Old Nick (Sean Bridgers), who routinely enters the room to rape the mother while the child sleeps in a small closet.

Though not without its fair share of sentimental moments, Room mostly lets its characters navigate its dramatic-yet-relatable emotional journey in an organic way '€” and what characters they are.

Main actors Brie Larson (as Ma) and Jack (Jacob Tremblay) are mesmerizing, balancing brittleness and fortitude with subtle grace that endures throughout. Especially in the film'€™s first half, Larson evokes a disquieting amount of maternal devotion and endurance, displaying a facade of absurd normalcy in the face of constant bleakness.

The actress never sheds Ma of her fear, yet simultaneously imbues her with a purposeful amount of love that seems to be as much for her own sanity as it is for her son.

Tremblay is equally spellbinding as a 5-year-old (the actor was 8 during production) '€” sometimes brattish but without coming off as annoying, sometimes lovely without being cloyingly so.

What makes the main characters so affecting is the realism and subtlety of their acting.

Then there is the room itself. A self-contained 11-by-11-foot universe of grimy seclusion, it is actually a shed filled with a single bed, an old TV, a tiny kitchen, a closet and a bath. Cinematographer Danny Cohen stylishly captures the room, mostly from the perspective of Jack '€” a child full of wonder at his surroundings, and dependent entirely on his mother for his image of reality.

Jack, a child conceived when his mother was raped by Old Nick, and who was born inside the room, has grown into a boy who knows the world only as described by his mother '€” that the room is the only thing that is real, and that everything else only exists on TV.

Director Lenny Abrahamson (who directed the award-winning Frank two years ago) captures Ma and Jack'€™s moments at his usual patient pace, establishing his characters'€™ bizarre existence clearly alongside Cohen, whose camera work follows the size of Jack and Ma'€™s world '€” shooting tighter frames during the movie'€™s first, in-room, half, and gradually letting in wider shots for the movie'€™s later sections.

Abrahamson does sometimes let Stephen Rennicks'€™ score and Jack'€™s voice-over dominate when strong visuals would have sufficed. But that is a minor quibble.

Unsurprisingly, the film'€™s first section is its strongest. When Ma and Jack '€” mild spoiler alert, though it shouldn'€™t be considered as such '€” eventually escape, the film widens its focus on the two characters'€™ attempts at fitting back into the world.

The newer characters '€” Joan Allen as Ma'€™s mother, Tom McCamus as her new husband and William H. Macy as the father '€” have interesting perspectives of their own, but without the devastating background of Ma and Jack'€™s bond, they come off as dramatically less compelling to watch. Theirs could be another movie, but in this one, it falters.

It'€™s difficult to watch Room without feeling a sense of despair that a world can offer such evil for no understandable reason.

But the sorrow and grimness isn'€™t why Room is so affecting, it is that Abrahamson, though indulging sentimental moments in his film'€™s second half, manages to keep his focus on the love between a mother and her son, letting that joy build the over-and-underlying structure of his story. Room is a true love story set in a cruel, cruel world.