In April, 2008, a 42 year-old woman named Elisabeth Fritzl revealed to police that she had been held captive by her father in a concealed basement in the family’s home in Amstetten, Austria. In Room, Joy (Brie Larson) has been similarly imprisoned for years, along with her young son Jack (Jacob Tremblay), where they are forced to live in a small room with only a basic cooker, lavatory and basin. Every night, their captor Old Nick (Sean Bridgers) visits with food and to repeatedly rape the woman. As Jack turns five, the woman sets in motion a plan to escape.

The Fritzl case – and that of another Austrian, Natascha Kampusch, who was abducted and locked up in 1998 – was also the source for Michael, Markus Schleinzer’s film about a paedophile who keeps a child imprisoned in a dungeon. Room, adapted by Emma Donoghue from her novel, lacks the merciless, desolate quality of Schleinzer’s film; both book and film focus on events from Jack’s perspective, inside the room and, later, in the wider world. It is a risky move that could potentially declaw the unfolding horrors of Joy and Jack’s situation; but fortunately Abrahamson steers his film away from mawkish sentiment.

It is essentially a robust, clear-eyed drama; one that delivers its few moments of cathartic lift with intelligence. Larson is tremendous – a vibrant presence in Short Term 12 and Trainwreck, she proves herself equally adept here, where she is required to remain cramped both emotionally and physically for a substantial amount of the film’s running time.

Last year, Abrahamson directed Frank – an unconventional biopic of Frank Sidebottom, himself an unconventional musician. In Abrahamson’s view, Sidebottom could only find freedom while wearing a cumbersome papier mache mask; in Room, there are similar ideas of social exclusion and life at the edges.