"The Shadow Children" is a series of books written by Margaret Peterson Haddix. The story is set in a dystopian society where families are only allowed to have two children due to overpopulation. As a result, any additional children are considered illegal and must live in hiding, known as "shadow children." The main character, Luke Garner, is a third child who struggles to survive in a world that forbids his existence. Throughout the series, Luke and other shadow children face challenges as they seek freedom and fight against the oppressive government that enforces the two-child policy.