The toxic atmosphere that once forced what remains of humanity below ground and made many of them infertile has, after ninety generations, become hospitable. Those strong enough, Settlers, venture Above to aid the survival of the citizens in the Sanctuaries Below. Trained to become a Settler since childhood, Graham's dream of living Above with his lover Cole is shattered when his medical test comes back with damning results: he is fertile. With the human race close to extinction, Graham is duty-bound to breed, forcing him and Cole apart.  Misery is followed by fleeting happiness once Graham and his assigned partner's daughter is born. But loss and grief, hatred and resentment soon follow, leaving all of them uncertain of what their futures hold.  Will he and Cole get the chance to live the life they want together, or will they be kept apart until Graham fulfils his duty?