Lenny Abrahamson’s ‘Room’ is an unsettling yet richly moving portrayal of a horrendous human tragedy. Taking a sadly familiar set of circumstances, the filmmaker creates a hopeful tale of two young lost souls who somehow manage to come out the other end of something that should have destroyed them.

Brie Larson stars as a young girl who was kidnapped at 17 and imprisoned in a room by a disturbed man (Sean Bridgers). At first, the circumstance is explained almost wistfully through the eyes of her son (the remarkable Jacob Tremblay), who was fathered by her captor against her will. The boy has never exited the confined space in his young life. He’s been taught by his mother to believe that the room is all that exists. Their TV broadcasts are visions from other planets, while their food is provided a mysterious man whom the boy must hide from in a closet when he makes a weekly visit to drop off supplies and rape Ma. Abrahamson never leaves the confined space for the first 40 minutes of his film, but somehow manages to give it a unique sense of life through the eyes of the child.

Eventually, Ma sees a means of escape and heartbreakingly must tell her son the truth about the world before hatching a plan for the boy to get out and seek help. From there, the movie is about their struggle to reintegrate into the world and into Ma’s family (Joan Allen, William H. Macy and Tom McCamus).

For the most part, Abrahamson sits back to let his actors dictate the movie. Larson delivers an extraordinary performance full of pain and understated warmth that feels like a breakout turn in her career. She’s matched by Tremblay’s wonderfully intuitive work, which is easily one of the best child performances in recent years. Veteran character actors provide strong support around the edges, but the movie belongs to the central duo and is defined by their relationship. Thankfully, they’re both presences fascinating enough to sustain the running time.

Occasionally, the filmmaker reaches for visual flourishes to elevate the character study, like the blown-out photography and shifting focus of the sequence in which the young boy’s eyes adjust to sunlight for the first time. The film likely would be stronger if Abrahamson pushed this visual expression further and more consistently. Likewise, there are times, particularly in the film’s last act, when the themes and messages are hammered home a little too hard compared to the more subtle strengths elsewhere.

Fortunately, any weaknesses in ‘Room’ are minor and don’t detract from the devastating overall power of the piece. The film is a disturbing and difficult experience worth seeing for the stunning central performances alone.