The story takes place inside an old city in a fictional universe where the nights are plagued with evil beings. A demon hunter receives an imperial order to hunt demons. In an instant, members of the imperial family and public officials are mysteriously killed. Angered by the deaths, the King orders Yan Li to use his life as a wager and ensure that he will hunt down every last demon. Facing pressure from all sides, Yan Li is forced to risk everything in a battle of wits and will with the demons. As the truth draws near, the stakes also grow higher, and Yan Li becomes embroiled in a fight between humans and demons that greatly impacts his life, his reputation and his love.