At a time when stepping outside could kill you, Harry is kept indoors at all costs, never venturing beyond the entrance to their building, never knowing the truth of how he came to call this place home. Bodies continue to build up around them, inescapable layers of toxic dust hang heavily in the air and Katie is only getting sicker. Then, after years without human contact, Katie and Harry are terrified by the arrival of another survivor and Katie knows she must finally undertake a previously unthinkable journey in search of the man she was supposed to marry.
In search of a new life for her son. Outside their safe haven, Katie and Harry encounter a world that is forever changed. There are new threats to their safety here, fellow survivors who are determined to start a new population, to save the world they so desperately misunderstood.
Katie is pushed to unimaginable lengths as she pushes ahead in search of a better life and as Harry's safety wavers in the balance. As they travel further north, leaving their once safe haven so far behind them, Katie knows how much harder it will be to return if things go wrong.