On his fifth birthday, Jack wakes up next to Ma inside Room—the 11-by-11 shed that Jack has called home all his life. As Jack and Ma celebrate his birthday by reminiscing about the day of his birth, baking a cake, playing games, and watching TV, it becomes clear that Jack and Ma are captives of a man they know only as Old Nick. Jack is Old Nick’s biological son, and Ma, who has been locked up in Room for seven years since she was abducted at 19, is just barely keeping herself and Jack alive—and sane. Ma is just 26, but already suffers from a bad wrist as well as rotting teeth and a barely-controlled addiction to “killers,” which results in her having “Gone” days where she is unable to get out of bed. Many of the things Jack and Ma do together are things that Jack perceives as games—but actually, activities like “Orchestra” (banging on objects and walls), “Scream” (screaming as loud as they can at the skylight), and flicking the lamp on and off again are designed to draw attention to the isolated hovel Ma and Jack are forbidden from ever leaving. It also becomes evident that Jack believes no world exists outside of Room—Ma has told him that beyond Room, there is only Outer Space, and that the things they see on TV are fake things happening on “other planets.” Though Jack has a limited understanding of reality, he has a tremendous vocabulary, a clear moral center, and is beginning to want more out of life (such as toys and animal friends). Old Nick comes to Room several nights a week to bring by food and to rape Ma—every time he enters, by way of a heavy door sealed by an electronic keypad, Ma hides Jack away in Wardrobe so that Old Nick can’t see him, and so that he can’t see Old Nick.
Shortly after Jack’s birthday, a series of things happens that shift Jack’s understanding of Room—and the world beyond it. First, Jack witnesses Old Nick choking Ma one night. Next, Jack sees an advertisement for Ma’s “killers” on TV, and begins demanding to know if some things on TV are real. Third, Jack finds a mouse alive in Room, and starts to understand that there are other creatures just out of reach. Ma begins trying to tell Jack more about the world—and the circumstances of her abduction—by telling him fantasy stories, but the sensitive Jack is disturbed by Ma’s tales and confused when she tries to compare herself to Alice in Wonderland. One night, Jack overhears Old Nick tell Ma that he has been out of work for six months and is struggling to pay the bills. The conversation intrigues Jack, who climbs out of Wardrobe in the middle of the night to look at Old Nick. When Old Nick wakes up and tries to talk to Jack, Ma flies into a rage and begins screaming. As a punishment for Ma’s infraction, Old Nick cuts the power for several days. Ma and Jack grow colder and colder and nearly run out of food, leading Ma to realize that she must do something to change their circumstances before Old Nick does something even worse. Ma begins telling Jack about her abduction and the world outside Room in more concrete terms, and though Jack grows more and more confused about what’s real and what’s not real, he slowly begins to grasp their situation. Ma begins preparing Jack to attempt an escape—an idea that exhausts and confounds Jack.
Once the power comes back, Ma enlists Jack’s help in crafting an escape plan. Jack suggests Ma use the very trick Old Nick used to lure her into his clutches so many years ago. Old Nick captured Ma by approaching her on her college campus and pretending he needed help with his sick dog—now, Ma realizes that if she pretends Jack is terribly ill, Old Nick will have no choice but to bring Jack to a hospital, where he’ll be able to ask for help. Jack insists he isn’t ready, but when Ma begs him to help her, he reluctantly agrees. Ma begins putting her plan in motion by telling Old Nick that Jack is starting to come down with something. The next day, she refuses to let Jack shower or flush the toilet and breaks his feces up with a spoon so that it looks like diarrhea. She presses a bag of hot water on Jack’s face as Old Nick’s arrival approaches, and even forces herself to vomit on Jack’s shirt to make him smell sick. When Old Nick arrives, Ma begs him to see how ill Jack is and to take him to a hospital. Old Nick, suspicious and apathetic, refuses to bring Jack to the ER, but tells Ma he’ll bring some medicine tomorrow night.
Jack tells Ma he’s sorry that the plan didn’t work. Ma, though, insists excitedly that they can now enact Plan B—pretending that Jack has died, and sneaking him out rolled up safely inside a rug. Jack is even more averse to this plan than he was to the first, but Ma convinces Jack that this is their last chance. Ma talks Jack through the new plan: he will be rolled up inside Rug and must remain very stiff as Old Nick carries Jack to his flatbed truck. Ma prepares Jack to jump out of the truck at the first stop sign. The next night, when Old Nick arrives, Jack listens as Ma tells Old Nick Jack has died and demands Old Nick take him far away to be buried. Old Nick agrees, and soon Jack feels himself lifted up into the air. Things go exactly as Ma said they would, but Jack has trouble unrolling Rug and misses the first two stop signs. At the third one, he jumps out—but Old Nick sees him and chases him. Jack runs headlong into a man walking his dog, and the dog bites Jack’s finger. As Old Nick catches up with Jack and carries him back to the car, Jack begins screaming—and the man with the dog calls the police. Old Nick drops Jack and drives away. The man, whose name is Ajeet, stays with Jack until the police arrive. A kindly cop named Officer Oh begins questioning Jack about what has happened to him, and though Jack struggles intensely both to understand her questions and to respond to them, Officer Oh remains determined to get to the bottom of Jack’s story. When Jack tells Officer Oh that he comes from a small room with a skylight that is, according to Ma, “not on any map,” Officer Oh and her partner do a satellite search for freestanding structures with skylights in the area and successfully triangulate the location of Room. The officers quickly drive there, free Ma, and reunite her with Jack. As Ma and Jack embrace, Jack says he wants to go back to Room and go to bed. Ma tells Jack that they are never going back to Room, and Jack begins sobbing.
After a visit to the police precinct to give a statement to the police captain, Ma and Jack are driven to a nearby psychiatric clinic for evaluation, care, and rest. They are swarmed by paparazzi at both the precinct and the clinic—the media has already gotten ahold of their story. A kind doctor named Dr. Kendrick collects a rape kit from Ma and cleans Jack’s scrapes and dog bite, and a psychiatrist, Dr. Clay, introduces himself as Ma and Jack’s primary physician. The exhausted Ma and Jack fall asleep as soon as they’re taken to their room, and in the morning, Jack awakes to an entirely new world. As he looks out the window at the city below, he can hardly believe the sight of so many people and buildings. Jack is confused when Ma throws their old clothes in a trash bin and takes a shower rather than a bath—before breakfast, which usually comes first. Ma tries to explain that they’re no longer bound by the rules of Room, but Jack misses the comfort of his old life. As Ma and Jack meet the hospital staff, attend therapy sessions, and receive medical care, Jack struggles with the new pace of his life. Ma and Jack learn that Old Nick has been sent to jail, and entertain visits from Ma’s mother, whom Jack calls Grandma, and Grandma’s new husband, Leo. Ma is happy to be reunited with her mother but sad that her parents are divorced and her father has moved to Australia.
As the days go by, Jack and Ma explore the clinic, but limit their outside time due to tthe paparazzi—and Jack’s emotional sensitivity to being outside. A lawyer advises Ma to consider either filing lawsuits against the media for using her image without her consent or submit to a major interview—she needs to secure a financial future for herself and Jack. Ma reunites with her brother, Paul, and she and Jack meet his wife Deana. Ma struggles to balance these happy reunions with her family with the challenge of keeping Jack away from media about their case and helping him process his intense anxiety about being “Outside.” Ma has some much-needed dental work done, renewing her confidence and restoring her sense of self, and she and Jack begin a nightly routine of counting all the friends they’ve made in the world so far. Things are derailed once again, however, when Ma’s father—Grandpa—arrives and can barely stand to be in the same room as Jack, whom he sees as an aberration. Ma consents to a major TV interview, but as the journalist asks her increasingly invasive and damning questions which frame her as selfish for keeping Jack in Room rather than asking Old Nick to take him to a hospital or shelter, Ma begins to break down. The day after the interview, Ma is “Gone,” and Jack is surprised that she still has Gone days outside of Room. Jack goes on an outing to the mall with Paul, Deana, and their three-year-old daughter Bronwyn. The trip is overwhelming and confusing, and when Jack returns to the hospital he finds that Ma is unresponsive. As nurses and doctors attempt to revive Ma, Jack notices that her bottle of killers is empty. Jack tells the unconscious Ma she’s had a “bad idea.”
While Ma recovers from her suicide attempt, Jack goes to stay with Grandma and Leo, whom he calls Steppa. Grandma and Steppa struggle to understand Jack’s peculiar way of talking, thinking, and seeing the world, and have trouble managing the intense separation anxiety he feels being away from Ma. Slowly but surely, Grandma and Steppa begin to get closer to Jack. Jack talks on the phone with Ma every couple of days, and though she assures him she’s getting better, they can’t see each other yet. Grandma and Steppa introduce Jack to playgrounds, LEGOs, potato chips, and even take him to the ocean for the first time, and Jack enjoys spending time with them more and more. After several weeks, Ma surprises Jack at the house one day—he is overjoyed to see her, and Ma is excited to tell Jack that they’ve secured their own apartment in an independent living facility with good security and round-the-clock counselors on staff. After they move, a shipment of things from Room arrives, and Ma and Jack get into a terrible fight about whether or not they should keep them. It’s clear that Jack still misses Room, which Ma resents. As the weeks go by, Ma and Jack spend time with family, try all sorts of new foods and activities, and make lists of the things they want to accomplish in the future. But Jack keeps bringing up Room and expressing a desire to go back. Eventually, Ma reluctantly calls Officer Oh to ask if she’ll escort them on a visit to Room one last time. The next day, Officer Oh brings Ma and Jack over to Old Nick’s and leads them to the backyard, where they face down Room. Jack marvels at how small Room is and asks if it has “got shrunk,” but Ma insists it’s the same size as always. Ma helps Jack bid goodbye to all the objects inside Room, and then, together, they leave it behind once and for all.