Room begins with a ripped-from-the- tabloids premise and then systematically rejects every bit of conventional wisdom regarding how that premise might unfold. The headlines write themselves: "Shed Boy's Daring Escape," perhaps, or "Captive Teen Mom Risks Everything to Save Rape Baby."

These headlines are accurate, technically: Room is about a boy who is born in the garden shed where his mother, "Ma" (Brie Larson), has been kept captive for seven years, ever since she was abducted at age 17. Five-year-old Jack (Jacob Tremblay) has never seen the world outside of the shed—he doesn't even know such a world exists—and when Ma decides that Jack is finally old enough to help carry out an escape attempt, the plan she concocts is dangerous and thrilling.

But there's much more to this story than the headlines. Room is based on a 2010 novel of the same name by Irish Canadian author Emma Donoghue. I read the book in one sitting—in a paroxysm of anxiety and emotional investment that kept me awake until 3 a.m.—and came away impressed by its thoughtful, unexpected treatment of the incredibly disturbing subject matter.

The film succeeds by the same token. With a screenplay written by Donoghue and helmed by little-known Irish director Lenny Abrahamson, it's a surprisingly faithful adaptation that trusts the strengths of the book will shine on the screen. And they do!

For the first five years of his life, the shed—the "room"—is the only world Jack knows. The shed's skylight is a portal to outer space; the television is a world unto itself, where Dora the Explorer looms large. Guided by his mother, Jack plays games, does exercises, learns his manners, and generally acts the part of a curious, active 5-year-old—who happens to be imprisoned in a rape shed.

A less sensitive, less ambitious film might have focused on their captivity, on the rape scenes, on the brutality of their captor, thereby ratcheting up the tension for two hours until mother and child make their triumphant escape. Room is better than that—and mercifully, it cuts the tension halfway through. It's no spoiler to reveal that Ma and Jack escape from the shed. (And knowing that their freedom is imminent in no way diminishes the tension of their escape—that shit is harrowing.) The second half of the film deals with their return to the outside world: the challenges of assimilation and introducing Jack to literally everything, as well as pressures from family and the media. Ma must confront her own trauma once Jack no longer depends on her for every aspect of his survival, while Jack struggles to contend with the overwhelming reality that the world is much, much bigger than he imagined.

Most of the movie is from Jack's perspective, and Jacob Tremblay is a rare non-annoying kid actor who carries his scenes with vulnerability and charm. Voice-over narration from children should be illegal (it's basically a war crime), but otherwise Tremblay is refreshingly natural, particularly when he's just being a kid—jumping around the shed, playing with his toys, annoying the bejesus out of his mother. There's a plausible intimacy between Tremblay and Larson, who gives a restrained, internal performance as a mom who is determined above all to raise a safe and happy child.

Room rewards a close viewing as well as a casual one—watch it as a sensitive and insightful character study, and notice the care Ma puts into turning the shed into a home for her son, the well-drawn family dynamics straining what should be a happy reunion with Ma's parents, the depression Ma suffers after she escapes. Or watch it for "Daring Escape from Rape Shed!"—the action sequences are about as tense and nail-bitey as it gets. Either way, it works.