Ghost master He Si Mu has lived for four hundred years, standing strong as the most powerful female spirit lord of Guixu, a realm of spirits. On a brief excursion, she runs into young mortal general Duan Xu, who happens to possess an heirloom that once belonged to someone from her past. Intrigued, the two begin to subtly test each other, hoping to lure out hidden truths behind their first impressions. Si Mu begins to understand Duan Xu's history and his deep ambitions, while Duan Xu is touched by Si Mu's unwavering resolve despite her immense loneliness. They decide to forge an alliance to keep both the human and spirit worlds safe – but what happens when an immortal and a human fall in love?