It's Jack's fifth birthday. He's spent the last five years inside of Room, which is, well, a Room. We'd have chosen Chuck E. Cheese for our fifth birthday, but whatever.
Jack lives in Room with his Ma (and other objects like Chair, Rug, Skylight, Door, and more) Every day, they bathe, eat breakfast, play, learn, eat lunch, scream at Skylight, nap, watch a little TV, and eat dinner. Then Jack goes to sleep inside Wardrobe. No, it doesn't take him to Narnia. If he knew about Narnia, we think he'd totally try to go there, because most nights a man called Old Nick comes in, gets in bed with Ma, and makes some creaky noises. Um, something's not right here. A lot of things aren't right here. Nothing is right here.
Ma hides Jack from Old Nick, but Jack starts acting out. When he uses the remote-controlled Jeep Old Nick got him for his birthday in the middle of the night, it scares Old Nick and he hurts Ma, leaving bruises on her throat. Ma eventually reveals to Jack that Room is a place where she's been kept ever since she was kidnapped seven years ago. Whoa. If we hadn't read the back of the book, we'd never have seen that coming.
When Ma discovers that Old Nick lost his job, she's afraid he'll abandon the house... and she and Jack will starve to death. She concocts a plan to escape: Jack will pretend to be dead and get rolled up in Rug. Old Nick will bury Jack far from the house. Jack will escape when Old Nick stops at a stop sign.
The plan actually goes off with nary a hitch. Old Nick almost catches Jack, but a man walking his dog and young daughter scares Old Nick away and calls the cops. The cops wrangle information out of Jack, who is terrified to be Outside. They find Ma and catch Old Nick.
Just kidding. The whole second half of the book is a series of events in which Ma and Jack try to adjust to society. Seven years is a long time for Ma, and Jack is seeing things that he thought only existed in the TV. They stay at a Clinic where they are treated by Dr. Clay and his nurse, Noreen.
Ma reunites with her family, namely her mother and new stepfather. Their relationship is a little chilly. Ma and Jack also get to know Ma's brother, Paul, and his wife and daughter. After an emotionally trying talk-show appearance, Jack goes to the mall with Paul and his family. When they return, Ma has attempted suicide by ODing on pills. Jack goes over the river and through the woods (or at least down a few city blocks) to Grandma's house until Ma recovers.
When Ma gets out, she and Jack move into an apartment by themselves. Jack wants to go back to Room, and Ma eventually agrees to take him there one last time. They see Room, and Jack says goodbye to it. He closes the door on that chapter of his life, and gets ready to start a new one.
The end. For real.