The Government is cutting down the woods near Luke's house in order to put up a housing complex. This is a major problem for Luke, who has never been outside of his family's yard because of his status as a Shadow Child: he is a third child in a world where the Government only allows families to have two children. His parents, who are simple farmers, must keep his existence a secret even from members of their extended family, their friends, and their neighbors.
Twelve-year-old Luke is used to being told when to hide, and he has always obeyed his parents' warnings to stay out of sight. He lives in the attic, plays with his brother's toys, and reads his family's few books. However, when the woods are cut down, Luke loses the ability to even go outside. Because of the increasing number of people walking around his house, Luke's parents agree that he can't go outside. His only freedom is to peer out through the vents of the attic at the construction of the new housing complex, which will become a home for Barons, the country's wealthy elite.
Circumstances become more dire for Luke's family. The Government takes away their ability to raise hogs, which are a major source of the family's livelihood, and raises their taxes at the same time. This leads Luke's mother (the person he is closest to) to take a job in a factory in order to make ends meet, which means that Luke now spends most of his days alone and confined. He pushes back against his confinement by going downstairs when his family has left, but his father yells at him for taking this risk.
Peering through the vents at the new neighborhood of Barons, Luke notices something strange: a child's face in the window at a time when everyone is gone. Other strange sightings around the house convince Luke of the possibility that a third child like him might be living there, and he decides to go over their house and knock at their door. He is met by a young girl his age named Jen, who at first mistakes him for a robber. He soon finds out that Jen is a Shadow Child like him, and that she runs an internet forum for other Shadow Children. Because of her status as a child of a Baron family, Jen has access to technologies like the internet and special snack foods, and she can even leave the house due to fake identification that her parents have obtained for her.
Luke begins to visit Jen as often as he can whenever his family is away. She teaches him about the corrupt actions of their Government, which created the Population Law limiting families to only two children despite the fact that it would be more effective to distribute resources more equally. She also tells Luke about her plans to stage a rally in which Shadow Children show up on the lawn of the president's house. It is Jen's hope that taking the Shadow Children out of the shadows will force the Government to recognize them and give them more rights, but Luke is skeptical about this plan. When he voices his disagreement, Jen kicks him out of her house.
The night before the rally, Jen sneaks into Luke's house and tells him goodbye. When he says he'll see her when she gets back, she doesn't reply.
Days pass and Luke hears nothing about the rally on the radio. He also sees no signs of Jen. After a week, he sneaks over her house and is surprised by a man with a gun. It turns out that this man is Jen's father, and he informs Luke that Jen and the few dozen other Shadow Children who attended the rally were all gunned down and killed. Jen's father also informs him that he is a member of the Population Police, and he hides Luke in a closet when other members of the Population Police visit.
Jen's father is able to get Luke an ID from a young Baron child who died, so Luke assumes this child's identity and attends boarding school in his place. Luke says a tearful goodbye to his parents. He vows to get an education and find ways to change society and create a place for Shadow Children, just as Jen would have wanted.
