The story of a mother and her young son held captive in a shed by a sexual predator, Room is a most extraordinary achievement, finding light and love and hope in even the darkest of places.

Based on Emma Donoghue’s best-selling novel, which she adapted into the film’s screenplay, Room has the makings of a psychological nightmare, with Ma (Brie Larson) a 20-something sex slave to an older man, who abducted her as a teenager, impregnated her, and now keeps mother and son imprisoned in a single-room space with a toilet, bathtub, stove, fridge, bed, and a metal door locked tight.

Despite the title, the film is less about this horrific ordeal as it is the unbreakable emotional bond forged between Ma and her 5-year-old son Jack (Jacob Tremblay) by their dire predicament.

Room is the name Mother and son affectionately call their prison, the only world Jack knows, other than the jumbled, static-y images of people and places he sees on a small TV; the blue sky and seasonal changes he observes in the small skylight above, and the conjugal visits by his father with his mother, the man he calls Old Nick (Sean Bridgers).

Room is quite literally all Ma and Jack have. It’s also only part of their story.

A cursory glance at Room’s IMDB.com page reveals the film’s cast as being much larger than the trio of actors already mentioned, so it’s no spoiler to say Ma and Jack do escape. But freedom doesn’t bring closure or peace, as room proves difficult to escape in other ways.

Reunited with her mother and father (Joan Allen and William H. Macy) who long thought their daughter dead, Ma struggles to readjust post-room. While her life was put on hold, others were forced to carry on and with varying degrees of success.

For Jack, though, the transition to his new life goes much more smoothly. And so caretaker roles are reversed as the young son must now be a parent to his damaged mom.

Donoghue’s story boldly marches into these and other unexpected places, making Ma and Jack’s ordeal all the more compelling and haunting. War is only part of a soldier’s story, after all, and it’s their struggle after returning home that often truly showcases the human and heartbreaking elements of the tale.

Larson, who is nominated for an Academy Award for Best Actress for this emotionally turbulent role, is the film’s beating heart, the strong, protective mother who finds herself broken and in need of repair. Ma’s warmth, humor, love, fear, and hurt connect with us effortlessly from the screen with Larson’s performance as authentic as it is natural.

While the 26-year-old actress is not a new face in Hollywood, Room is clearly her breakthrough performance — just as 2010’s Winter’s Bone was for Jennifer Lawrence — particularly for those who have never seen her terrific turn as a teen counselor struggling with her own issues in 2013’s indie film Short Term 12.

Equally impressive is 9-year-old Tremblay, with an astonishing performance as true and fully formed as those delivered by any actor this year. Jack and his childlike devotion and optimism are the soul of Room, with Tremblay’s twinkling eyes and hopeful smile brightening even the darkest of moments on screen. Larson and Tremblay are even better together, selling their mother-son relationship convincingly.

Of the other actors, Allen has the biggest role, and the actress makes the most of it as a middle-aged mother struggling to make sense of her daughter’s return — and the fact that she is now a grandmother.

How does the return of a daughter long thought dead affect the stability of a family that has moved on? And how does the daughter react to that? Room explores these and other facets of similar-but-true accounts — issues most of us never consider after the inevitable network-exclusive interview with the abductee and the family. And, yes, Room even touches on that. The film is quite thorough.

Room was directed by Lenny Abrahamson, who is best known for the quirky-odd and under-seen Frank, a comedy-drama about a band leader (Michael Fassbender) who wears an oversized mask. Room is even less conventional — particularly with its limited setting and scope. And even when it does jump out of its confined space, Room’s characters often appear as if they’re boxed in by their surroundings.

Room is a tricky if not delicate film, with a dark subject matter that could easily tip over as overly horrific or even hammy. Abrahamson, who also is nominated for Best Director,  steers the material and the performances far away from such trouble-spots, and finds a rhythm of emotions that make Room touching and powerful.

This isn’t a story of imprisonment but of survival, and how family, courage, hope, and love help us carry on, even through the darkness.

Contact Kirk Baird at kbaird@theblade.com or 419-724-6734.

First Published January 22, 2016, 5:00 a.m.