Josh Overstreet and his sister Claire have been carving a life out of the ash for more than half a decade, unsure whether anyone yet lives outside the small valley where they have established their town of Overstreet with two dozen others. Then Deanna Pembleton stumbles into the valley, asking for help for herself and her friends. Claiming they have eked out a life much like that of the people of Overstreet, she begs assistance, which Josh is willing to give. She is, however, clearly unhinged on some level. Could the people she is claiming to want to help just be figments of her imagination? Against the advice of almost everyone in Overstreet, Josh and Adaline set out to try and take food to Deanna's people, hoping that people still exist outside "the last valley." They never dreamed their valley might not be there for them when they get back.