Lumi, a young girl, is building a fort in the woods to cope after her mother's death. With her mother's passing, Lumi finds it unbearable to live with her father because he spends all day drinking. Additionally, her brother Ty has left the house, leaving Lumi with no support. As she's constructing her fort, a man named Jack appears, revealing that she is on his property. Jack then tells her that she is building her fort incorrectly, and he teaches her how to construct it properly.

The next day, Lumi attempts to build a fort away from Jack's property. Jack once again comes over and inspects her work. He tells her she has improved and asks if she wants to see his fort. She agrees and is amazed at how impressive his fort is. It is a dugout, and he can sleep in any weather. Lumi asks if he has a house, and he says he does. Lumi asks why he builds forts, and Jack states that he wishes he knew. Lumi returns home to her drunk father and declares that she will go camping. Her father tells her to use the tent in the basement, but Lumi camps in her homemade fort instead. As the weeks pass, Lumi sleeps or stays in her fort whenever she can. Jack appears now and then to teach her more survival skills, and soon she learns how to boil acorns and make fires. When her brother Ty returns home, Lumi is excited. She tells Ty about the fort and Jack, but Ty is concerned. He's heard rumors that Jack is a strange man.

After Jack's wife dies, he lives in his dugout in the woods. However, Lumi continues to visit the man. Ty returns home, and Lumi continues to see Jack. When the snow starts to fall, Lumi asks Jack to teach her how to make a snow trench. Instead, Jack gives her a waterproof tarp and tells her he is leaving and does not know if he will come back. Jack then says that he can build her a dugout, and Lumi demands that the dugout be built next to his. Jack agrees, and they create a dugout. Lumi asks when he's leaving, and he replies that that he will leave at the crack of dawn. They sleep in their dugout, but Lumi gets cold and crawls into the man's dugout. The man keeps her warm, and Lumi tries to stay up to watch Jack, but she falls asleep. When she wakes up, Jack is gone, and she hears Ty calling out for her. She then remembers that Ty was going to be coming this week. She runs into Ty's arms and begs Ty to let her live with him.