Never leave someone behind: it's a promise easier made than kept, especially when seventeen-year-old Pip takes the headstrong twelve-year-old Iris under her protection in the wake of an earth-shattering plague. After an unspeakable tragedy, the duo must navigate the nearly unrecognizable remains of Spokane, facing roving slave traders, merciless gangs--and worse. Pip and Iris soon meet Fly, a stubborn and courageous older girl, and as the three grow closer and their circumstances grow more perilous, they must also grapple with their own identities in this cruel new world. Pip's vow to never leave someone behind may have made survival more difficult for her, but this promise could also be the key to finding meaning in the ashes of what came before.