This is book number 3 in the Shadow Children Books series.
Nina Idi -- a third child in a society where families are allowed only two children -- has been betrayed by the boy she loved, and arrested by the Population Police for exposing other alleged third children. Angry and confused, Nina knows only one thing for sure: She is innocent of the charges. But now she is faced with the most difficult choice of her life: Get three other prisoners to admit they are shadow children and be spared herself, or refuse to cooperate and be killed.
The options are clear. The choice, Nina discovers, is not....