To save his close friend Wu Qian, Xu Shan reveals his secret of immortality, only to be kidnapped by Wu Qian and taken to Snake Island, where Wu Qian intends to steal his destiny and lifespan. However, Wu Qian never imagines that Su Zhen, the ruler of Snake Island, is actually Xu Shan's ex-wife. Five hundred years ago, Su Zhen rescued Xu Shan after he was severely wounded by bandits on his way to take the imperial examinations. The two fell in love, but because humans and demons belonged to different worlds, Xu Shan eventually left her. Before he departed, Su Zhen placed a curse on him, making him eternally youthful and immortal.