High school student (and 15 year old) Joe (Nick Robinson) lives with his father Frank(Nick Offerman). Joe has constantly had what we call "daddy issues" right after his mother had died. He has an older sister Heather (Alison Brie), but she is engaged to Colin (Eugene Cordero) and is out of the house. There is a lot of tension between Joe and Frank which is also seen one night when the family gathers to play Monopoly, like they used to do when Mom was alive. Joe didn't want to play anyway, he wanted to go to a party with his friends. After a fight with his dad, Joe ends up calling the police, claiming "Theft" (due to his loss in monopoly). After a scuffle Joe leaves his house to attend a party with his friends. Here we see that Joe has a crush on his friend Kelly (Elin Moriarty) but the Kelly is already in a relationship with her boyfriend Paul. Due to some unusual events, Joe and an unusual named Biaggio (Moises Arias) get lost coming home through the woods. They come upon an open glade, dark and mysterious in the moonlight, so beautiful that the two boys stop dead in their tracks. Joe gets the idea to remove himself from his father's home, and build a house in the woods with his best buddy Patrick(Gabriel Basso, also having parent issues). Joe, though being skeptical of Biaggio, can't ask him to leave as he is too shy of it. Hence Biaggio sticks along with them. Patrick stashes up on survivalist books from the library, treating the project seriously, liking the image of freedom and manliness that Joe paints for him. They draw floor plans, they plunder materials from construction sites, they spend their days out in the woods building their house. And then, one night, all three sneak away from home and move in.
The community, of course, thinks they may have been kidnapped. But the police has enough evidence to prove that Joe, Patrick and Biaggio have consensually moved out without their parent's consent, leaving with a few thousand dollars some food and tools.
Meanwhile, out in the woods, the three boys revel in an unfettered life, trying to catch fish and other critters, so that they will be entirely self-sufficient. Joe makes many speeches about masculinity. Joe and Biaggio are in charge of hunting while Patrick usually gathers food. On the quest of hunting (which they both aren't capable of) Joe and Biaggio stumble across a supermarket far off the woods. Here they get the idea of "buying" chickens as they couldn't hunt.
Weeks pass by and they are living in the wood merrily, having adventure, playing songs etc. We see that Joe starts to miss Kelly. So one day he goes and invites Kelly to their lair secretly. Due to some turn of events Joe comes to know that Kelly has broken up with Paul and is now single, much to the joy of Joe. Kelly brings 2 of her friends in to the lair and all of them have a happy time together. Here we see Kelly bond with Patrick, which Joe refers to as her ignoring him (Joe) cuz she likes him. But he is taken aback that night. During their sleepover, Kelly comes to Joe's and Patrick's room and asks Patrick for a walk (not knowing that Joe is still awake). Joe has an emotional breakdown as the girl of his dreams starts dating his best buddy.
Things start to go bad with them when Joe purposely trap Patrick in a monopoly game, with Patrick referring to his relationship with "it just happened ... get over it!". Joe yells at Kelly that she is a bitch. Kelly leaves their house and Patrick apologizes to Joe for what happened between him and Kelly. Joe tells him to leave and then confronts him. After a scuffle, Patrick breaks a portion of the house and leaves furiously. Joe also asks Biaggio, who had stuck with him through all the hardships, to leave too. Both Patrick and Biaggio go to their home. Biaggio is taken to the police for questioning but they aren't able to take a word out of him.
Joe starts to get low on money to buy chicken. So he actually goes on a hunt and kills a rabbit for dinner. It has been 4 weeks since Joe left and the media are covering the news very seriously. Feeling responsible, Kelly goes to Frank and tells him about Joe's secret hideout. Meanwhile, due to the unhygienic condition of the house, Joe attracts a vicious snake (presumably a copperhead). He is trapped inside the house due to the snake when Kelly and Frank enter the house, to his surprise. This gets the snake startled and starts to go for Kelly. But Biaggio with a big combat knife enters the scene to kill the snake. Unfortunately, he is bit by the snake and is rushed to the hospital.
In the final scenes, Joe cleans himself up and has a talk with Kelly. She says that she cares about him alot, though they are not dating. Hence, they reconcile. But things are not the same between Joe and Patrick yet. Just before the credits, it seems that they have reconciled when both of them flash their "fingers" to each other and laugh it off.