Among the Free is the book that draws Margaret Peterson Haddix's Shadow Children series to a satisfying resolution.
The novel opens with illegal third child Luke Garner and his illegal friends, Trey, Nina, Matthias, Percy, and Alia, all working undercover at the Population Police headquarters to try to sabotage the totalitarian government from within. Luke works as a stable hand and is summoned by the sergeant for a special mission distributing new ID cards to citizens. When an elderly woman refuses to go to the village square to receive her new card and Luke disobeys his sergeant's command to shoot her, Luke unwittingly starts an open civil war between the villagers and the Population Police.
The moment Luke refuses to shoot, he runs off into the woods and goes into hiding for several days. He eventually makes his way into a village of starving people and meets Eli, who informs him that his village no longer cares about their own needs; everything they do is for the sake of caring for others in need, like Luke. The reason is because Eli's people were filled with such a horrid sense of guilt when they once turned in a family with an illegal third child for the sake of food. To demonstrate the villagers' devotion to ethics, Eli helps Luke escape the Population Police, and in so doing, Luke makes his way into another village where he sees that the citizens have finally overthrown the Population Police. However, upon returning to Population Police headquarters, Luke learns that former Population Police leaders already have plans to feed the public with propaganda that third children are responsible for all of society's ills and starving conditions, thereby taking back the government.
Luke gallantly stands before a news anchor and relays his entire life's story as an illegal third child, as well as the stories of his friends Trey, Nina, and Matthias. Their stories of hardship help persuade the people that third children are innocent and that the government is responsible for all suffering, securing freedom among his people.