Lenny Abrahamson’s latest movie after the quirky comedy Frank is a spine-chilling and ultimately moving tale of imprisonment and survival. Half of Abrahamson’s Oscar-nominated Room, based on Emma Donaghue’s acclaimed novel of the same name, is set in a confined square that gradually reveals its horrors. The sound-proofed space that serves as kitchen, bedroom, bath, toilet and recreation area is revealed bit by bit, in a skillfully measured escalation of horror.

This tomb-like prison with a single skylight is where Jack (Jacob Tremblay) was born and has lived his short life. His mother Joy (Brie Larson), the prisoner of a psychopath known only as “Old Nick” (Sean Bridgers) who lives above, has created an illusory world for her precocious son. The room is the only reality Jack knows, and it is imperative for Joy that she keeps spinning the lies, for the sanity of both. Jack believes that whatever world there is beyond the four walls is contained in the television set. The production design and cinematography brilliantly map out the corners of Jack’s world, while also creating a choking sense of claustrophobia that breaks only when Joy manages to trigger Jack’s escape.

The book was inspired by actual cases in the United States and Austria – in the latter instance, Elizabeth Fritzl was locked away and raped by her father and forced to have his children over a 24-year period. It’s hard to bring such heart-wrenching material to the screen without also letting in sensationalism, and Abrahamson retains the story’s emotional core by focusing on the prisoners rather than the prison guard. Nick remains a shadowy presence who visits at will and is removed from the movie just as suddenly as he appears.

Once Jack and Joy are over ground, the movie shifts focus and tone, as Joy’s parents (William H Macy and Joan Allen) try to help them readjust to normalcy. Much of the changes are seen from the point of view of Jack, and the subjective camera, often placed at his eye level, reveals his bewilderment at his new sensory environment. If Larson is overshadowed by Tremblay’s remarkable maturity in the first half, her character gains strength and layers in the second. The extremely convincing bond between the two is backed by admirable turns by Macy and Allen as Joy’s parents. The daughter that they lost is back, with a son who is the product of rape. Little wonder, then, that Jack sometimes feels that the “Room” is a safer and more predictable place, one where he had his mother all to himself.

Room has drawn inevitable comparisons with the harrowing German independent feature Michael (2011), which focuses on the relationship between a paedophile and a boy he kidnaps and locks away in his basement. Room does not recreate the horrors of confinement as effectively as Michael, and it becomes somewhat diffused once Jack and Joy are free. The rapid turn of events, mostly revolving around Joy, robs the narrative of its raw power and singular focus, but the powerful performances by Larson and Tremblay carry through the contrasting emotions of tragedy and hope.