Odds are good that audiences don’t know much about Brie Larson before stepping into a theater to watch the critically acclaimed drama Room.

Larson, who’s been a scene stealer in comedies like Trainwreck and an indie darling with Short Term 12, takes a major step toward stardom in director Lenny Abrahamson’s drama as Ma, a 24-year-old woman kidnapped and held in a shed for seven years.

Constantly raped by her captor Old Nick – played by an efficiently creepy Sean Bridgers – Ma’s world changes with the arrival of her son Jack, portrayed by the stunning Jacob Tremblay, who singlehandedly keeps Room from becoming too dark and twisted for a wide audience. The film will easily remind viewers on an emotional level of the famous kidnappings of Elizabeth Smart and Amanda Berry, but does not approach this fictional account on as harrowing a level.

Screenwriter Emma Donoghue – adapting her own 2010 novel for film – finds the right balance by placing audiences in Jack’s shoes, following the young boy as he lives in the only world he knows, unaware of the wide world outside nor how Ma came to live in the shed, which he simply calls Room.

The scene early in the film where Ma attempts to explain how things really are after years of tricking Jack is one of 2015’s five best moments in cinema. Equally touching and heartbreaking, Larson’s performance in this scene is what will likely lock up a win later this month for Best Actress at the Academy Awards.

Nine-year-old Tremblay is an absolute revelation as Jack, offering up the best performance by a child actor since Natalie Portman’s turn as a young girl taken in by a hitman in 1994’s Leon: The Professional. The entire film hinges on having Tremblay guide viewers through his world – which to audiences seems like a cramped room, but to Jack, is an entire universe.

Tremblay gives Jack such an authentic wonder and innocence that it’s impossible not to be taken in by Room, a film made with such finesse that otherwise dark subject matter doesn’t weigh down audiences.

The family dynamic between Ma and Jack works because of Larson’s undying commitment to follow Tremblay’s lead wherever the material takes them. The balance between the pair is refreshingly dynamic. More reaction than action, Larson plays off Tremblay with absolute ease and subtlety, offering harrowing realism to Jack’s childhood wonder.

As an audience member, there’s an immediate sense of constraint early in Room, but never to the point of feeling trapped, which is a massive credit to Donogue as writer, Abrahamson as director and Tremblay as performer.

The cinematic twist that occurs midway through Room, heart-wrenching and gripping as it may be, should be left unspoiled for first-time audiences, though the welcome addition of veteran character actors Joan Allen and William H. Macy in the second half of the film give Abrahamson’s film added dimension. Allen especially gives a gripping performance as Ma’s mother living outside of Room, providing a terrific emotional counter-balance to Larson.

Confined to such a small space, Abrahamson and cinematographer Danny Cohen make the world of Room come alive with nuanced camera work and production design that make individual elements of the room feel like their own worlds, reinforcing Jack’s attachment to individual items in the room like (in Jack’s words) wardrobe, sink, skylight and chair number one.

The use of ultra wide angle lenses when shooting inside Room allow viewers to see Jack’s world the way he sees it, allowing audiences to remember how the small places where children often grow up don’t feel small, but rather large to children.

When the entire world fits inside a 10 by 10 box, everything grows proportionally larger in scale. Pulling that off cinematically is a difficult thing to do, and the team of Abrahamson and Cohen nail it perfectly.

With a star-making and likely Oscar-winning performance from Larson, a tremendous young actor in Tremblay and subtle, effective direction from Abrahamson, Room is one of the 10 best films to be released in 2015 and a must-see in theaters before the Academy Awards on Feb. 28.