Darkness can hide in the brightest of places...Pickaxes, grime, and watery oatmeal are all sixteen-year-old Heart has ever known. Growing up in the tunnels, the only breaks in her muscle-aching monotony are the numerous nights spent cramped in a metal box. Stupid runaway mouth. But when strange visions and a hidden map hint there's more to life than she's been led to believe -- boys being one of them -- only one thing weighs on her mind. Escape.Yet freedom is a tease. Heart merely trades her small prison for a larger one -- a transparent dome controlled by the Guardian, an aging leader bent on creating a genetically perfect race. Heart's birthmark on her shoulder? An abomination that carries a lifetime sentence of slavery for females.Refusing to let a glass ceiling deter her, Heart searches for a way out of the dome. But unraveling the Guardian's secrets is a risky endeavor. Human skulls atop crude sticks serve as a warning: treason is punishable by death. When her new friends are captured, and escape is just an arm's reach away, Heart must decide. Take the freedom she so desperately wants or save her friends' lives?*For mature audiences over 16