The fifth book in Margaret Peterson Haddix's seven-book Shadow Children series, Among the Brave, features illegal third child Trey, who Luke Garner, another illegal child and protagonist of the series, befriended at the Hendrix School for Boys.
Trey is standing outside of Mr. Talbot's house, a double agent among the Population Police, who is actually working to free third children, when Mr. Talbot's house is raided by Population Police. Trey manages to hide and not be found. Once the raid is over, he sneaks into the house and discovers Mrs. Talbot. Together, the two watch news reports on television stating that the Population Police have just overthrown the government. Mrs. Talbot's response is to desert the house, leaving Trey to seek help by himself.
Trey grabs documents from the Talbot home that look vital and heads out. He makes his way to Luke Garner's old farm home where he meets Mark, an older brother of Luke. Believing Luke to have been captured by the Population Police, Mark sets out with Trey to find and rescue Luke.
During the quest, Mark is captured by the Population Police, and Trey must enlist as a Population Police officer using his fake ID card to try to free Mark. In his quest to find and release Mark, Trey runs into double agent Mr. Talbot, and together, they free Mark as well as Luke. Trey and Luke then escape to the safe house of Mr. Hendrix. At Mr. Hendrix's home, among the papers Trey had taken from Mr. Talbot's house, Trey finds a list of the names of 100 illegal third children. He forms a plan to continue working undercover as a Population Police officer to to track down the children and form a united front to overthrow the Population Police from inside the organization. Trey's friends agree to go undercover with Trey.