Among the Hidden is a captivating tale set in the near future, delving into the decisions and difficulties faced by a young boy trying to navigate a world where his very existence is against the law. Luke, a third child, resides in a society where families are restricted to having only two children. Because his parents violated these population laws by allowing him to live, Luke must remain hidden inside his home. He has never attended school, eats in the attic stairwell to avoid being seen, and spends his days with little to do but re-read a few old books and watch his neighborhood through the attic's air vents.

Upon discovering another third child, Jennifer Rose Talbot, who is also in hiding nearby, Luke takes the bold step of leaving his attic sanctuary. This leads him to uncover a network of hidden children who connect through Internet chat rooms. As Luke's friendship with Jen deepens, he learns that she is mobilizing the hidden children to protest the government's oppressive laws. He is then faced with the decision of whether to challenge the government and pursue freedom. In this futuristic dystopia, Haddix examines the impact of population control and other totalitarian government policies on individuals within that society, exploring the lengths to which a person will go to live a life worth living.