The apocalypse's dust blots out the sun, and the old world's order collapses. Why have two former lovers turned into enemies? Xu Chongan and Guo Jinyi travel together across the wasteland, evading packs of mutated creatures as they search for the fabled key that can restart civilization. Every step is a gamble with their lives, while the light and darkness within human nature clash fiercely in this desperate land.