On the eve of her wedding, Shang You, a young woman from the Holy Spirit Tribe, unexpectedly rescues Si Yuan, the Dark Lord of the Underworld Tribe. However, on her wedding day, her entire tribe is wiped out. To resurrect her people, Shang You disguises herself as Meng Li, a deer demon, and infiltrates the Underworld Tribe to steal the Dark Lord's Amber Heart. During their time together, she unexpectedly falls in love with her enemy. Despite this, she still chooses to take Si Yuan's heart to revive her tribe, only to later discover that her real enemy was someone else all along....