The story took place in two parallel universes named Yuan and Yi, where people shared the same life and death. Nian Yang Xiao, came from the Yuan World to save his true love Kong Ling Hui, crossed the border to the Yi World in search of the killer who assassinated his love. In the Yi World, however, he and Kong Ling Hui were enemies. Kong Linghui tried everything to kill him. At the same time, the mysterious girl Yong Er, the romantic street gangster, the cold-faced police officer Nuo Dun and others appeared one after another, each accompanied with a complex case. The involvement of Nian Yang Xiao made the cases more complicated and confusing.