Set during the late Qin dynasty or early Han dynasty, the film follows General Wang Sheng, a loyal and skilled military leader, as he leads an attack on a Xiongnu camp in the harsh desert. Amidst the battle, Wang Sheng encounters a mysterious and enchanting woman named Xiaowei. Unaware of her true nature, he rescues her and takes her back to his home. However, Xiaowei is no ordinary woman—she is a fox spirit that sustains her youthful beauty by consuming human hearts.
As Wang Sheng brings Xiaowei into his household, tensions arise between her and Peirong, Wang Sheng’s devoted wife. Peirong is deeply suspicious of Xiaowei, but Wang Sheng, unaware of Xiaowei’s true identity, sees no reason for concern. Meanwhile, another love triangle unfolds, involving Wang Sheng, Peirong, and Pang Yong, a former general who once fought alongside Wang Sheng. Pang Yong had loved Peirong in the past, but she ultimately chose to marry Wang Sheng, leaving Pang Yong with unresolved emotions.
Trouble brews as a series of gruesome murders begins to terrorize the city. Each victim is found with their heart removed, fueling fear among the citizens. Peirong’s doubts about Xiaowei grow stronger when a diviner warns her that Xiaowei is a demon. Her suspicions are further confirmed when she accidentally cuts Xiaowei but sees no blood. Determined to uncover the truth, Peirong turns to Pang Yong for help. Around the same time, Pang Yong meets Xia Bing, a young demon hunter who, despite her inexperience, is dedicated to her mission of eliminating evil spirits. Together, they set out to expose Xiaowei.
The true culprit behind the murders is revealed to be Xiaoyi, a chameleon spirit who harbors unrequited love for Xiaowei. Xiaoyi has been secretly acquiring human hearts to sustain Xiaowei, hoping to win her affection in return. On multiple occasions, Xiaoyi clashes with Pang Yong and his allies but always manages to evade capture. As tensions rise, Pang Yong and Xia Bing storm Wang Sheng’s house to confront Xiaowei, accusing her of being a demon. However, Xiaowei skillfully maintains her disguise, frustrating Peirong and Xia Bing.
As Xiaowei’s bond with Wang Sheng deepens, Xiaoyi grows increasingly jealous and launches an attack on Wang Sheng, but he is ultimately driven away. When Xiaoyi later pleads with Xiaowei to let him stay by her side, she angrily rejects him, insisting that she has no need for his love. This rejection devastates Xiaoyi, who remains obsessed with Xiaowei despite her cruelty.
One fateful night, Peirong stumbles upon Xiaowei shedding her human skin, exposing her true fox demon form. Horrified but resolute, Peirong confronts Xiaowei, leading to a tense confrontation. Xiaowei, sensing an opportunity, proposes a deal: she promises to stop killing if Peirong allows her to take her place as Wang Sheng’s wife. In a selfless act of sacrifice, Peirong agrees, hoping to protect her husband and the people of the city. Xiaowei then hands Peirong a potion, which, upon consumption, causes her hair to turn white and her appearance to become ghastly and unnatural.
The city’s inhabitants, mistaking Peirong for a demon, react with fear and aggression. A mob gathers, ready to execute her. Just as Peirong is about to be killed, Pang Yong and Xia Bing arrive in time to rescue her, taking her to safety in a secluded cave. However, Peirong’s condition rapidly deteriorates. Pang Yong and Xia Bing deduce that the potion she consumed is a fatal poison and that the lighter her complexion becomes, the closer she is to death.
Not long after, Wang Sheng, his soldiers, and members of his household—including Xiaowei—arrive at the cave. Faced with his wife’s apparent transformation, Wang Sheng swears that if Peirong is truly the demon responsible for the murders, he will kill her himself. At the same time, he openly expresses his enduring love for her. Moved by his devotion, Peirong takes a dagger from Wang Sheng and stabs herself, dying in his arms. Overcome with grief, Wang Sheng clings to her lifeless body, ignoring Xiaowei’s attempts to comfort him. It is in this moment that Xiaowei realizes that Wang Sheng will never love her, no matter what she does.
Seizing the opportunity, Pang Yong exposes Xiaowei’s true nature, attacking her with his weapon. However, her body proves to be as hard as steel, rendering his efforts useless. In desperation, Wang Sheng pleads with Xiaowei to bring Peirong back to life. Xiaowei, knowing that she now holds the power to have Wang Sheng for herself, asks him what he will offer in return. Wang Sheng replies that while he loves her, he already has Peirong. Accepting his fate, he then takes his own life.
Heartbroken, Xiaowei lets out a scream and reveals her true demon form. Despite the agony of her loss, she willingly attempts to bring Wang Sheng back to life, using the magical powers she has cultivated over thousands of years. As she prepares to sacrifice everything for him, she is suddenly interrupted by Xiaoyi, who seizes the magical orb containing her power. He chastises her for giving up everything for a human and insists that she return with him. Enraged, Xiaoyi swallows the orb and prepares to leave with Xiaowei. However, Pang Yong and Xia Bing refuse to let him escape and engage in a fierce battle. After an intense struggle, Xiaoyi is finally slain, but not before he mortally wounds Pang Yong.
With Xiaoyi defeated, Xiaowei retrieves the orb from his body, as well as another orb containing Xiaoyi’s powers. She then makes a final, selfless decision. Instead of keeping her powers, she uses both orbs to resurrect everyone who had perished in the battle, including Wang Sheng, Peirong, and Pang Yong.
As the film reaches its conclusion, Xiaowei is seen in her true form—a white fox, now powerless after giving up everything to save the man she loved. She walks away, knowing that her time in the human world has come to an end. Though she had spent centuries seeking love, she ultimately learned that true love is selfless, even if it means letting go.
The film ends with Wang Sheng and Peirong reunited, their love prevailing despite the hardships they faced. Meanwhile, Xia Bing, now a more experienced and wiser demon hunter, and Pang Yong, having found peace in his own journey, look toward the future. Xiaowei, once feared as a heart-eating demon, fades into the distance, her tragic tale leaving behind an unforgettable mark on those she encountered.