Catholic priest Sang-hyun begins his days at a hospital, offering quiet comfort and spiritual support to patients as part of his ministry. When a vaccine trial is opened to combat the feared Emmanuel Virus (EV), he volunteers to participate, hoping to help save lives. The procedure goes wrong, leaving him infected, but in a striking turn of fate, he recovers fully and almost instantly after receiving a blood transfusion. This miraculous healing spreads through his parish like a prayer taking flight, and soon his reputation as a healer grows far beyond his quiet parish walls.
As word of his recovery travels, thousands of people flock to witness the supposed miracle of his touch. Among the newcomers are Kang-woo, Sang-hyun’s childhood friend, and his family, drawn by the aura of hope surrounding him. Kang-woo invites Sang-hyun into his home for a weekly mahjong night, a scene that quietly intensifies the tension beneath the surface. At these gatherings, Sang-hyun finds himself unexpectedly drawn to Tae-ju, Kang-woo’s wife, a feeling that unsettles the careful balance of his life.
Sang-hyun’s life takes another drastic turn when he relapses into illness and succumbs to the need for sustenance in a way he hadn’t anticipated: he wakes with a new vulnerability to sunlight and a craving he cannot ignore. He begins drinking blood from a comatose patient, and the shock of his transformation unsettles him deeply. In a desperate moment, he attempts suicide, only to discover that the blood he craves still has power over him, and that EV’s symptoms recur whenever he resists feeding. To evade murder, he resorts to stealing blood transfusion packs from the hospital, a choice that darkens his path and accelerates the unraveling of his humanity.
Meanwhile, Tae-ju lives with her sick husband and a protective mother-in-law, Mrs. Ra, whose watchful eye frames much of the household’s atmosphere. Tae-ju’s quiet world is shattered when she becomes entangled with Sang-hyun, and when the truth of his secret comes to light, she withdraws in fear. In a bold, desperate moment, she suggests they kill Kang-woo so they can be together without the fear of exposure. Sang-hyun’s sense of duty clashes with his new desires, setting him on a road that will blur the lines between mercy and murder.
A higher authority within the monastery seeks vampire blood to heal his eyes so he can glimpse the world one last time before death. Disgusted by the request and the path it forces him to tread, Sang-hyun abandons the monastery and moves into Mrs. Ra’s house, intending to continue his affair with Tae-ju in secret. He notices bruises on Tae-ju and suspects Kang-woo, a suspicion she confirms, driving him toward a violent resolve. During a fishing trip with the couple, Sang-hyun makes a fateful decision to kill Kang-woo, dragging him beneath the water and concealing the body inside a cabinet in a house sunk at the lake’s bottom, with a rock to keep it from surfacing. When his EV symptoms flare again, he retaliates by killing his former mentor and drinking his blood.
As the police begin to investigate, Mrs. Ra’s condition deteriorates, her dependence on alcohol deepening as she remains haunted by the memory of Kang-woo’s death. Sang-hyun and Tae-ju are haunted by visions of Kang-woo’s corpse, and Tae-ju reveals the unsettling truth about Kang-woo’s treatment of her, which inflames Sang-hyun’s rage. In a moment of devastating despair, Tae-ju pleads for Sang-hyun to kill her so she can return to Kang-woo. He complies, but in a surprising turn, he feeds her with his own blood, reviving her as a vampire, and Mrs. Ra bears witness to the transformation.
From there, Tae-ju’s appetite grows, and she begins to kill indiscriminately to feed, while Sang-hyun remains more restrained, killing only when necessary. The ethical conflict between them erupts into a rooftop chase and a brutal confrontation. Mrs. Ra manages to alert Kang-woo’s friends to the truth: Sang-hyun and Tae-ju are responsible for Kang-woo’s death. Tae-ju kills two of the friends, and Sang-hyun appears to eliminate a third, illustrating the increasing danger of their coalition. Realizing the extent of the chaos they’ve unleashed, Sang-hyun urges Tae-ju to flee with him, and they escape in a car with Mrs. Ra as a witness to the night’s grim events.
Before they depart, Sang-hyun visits the camp of followers who once idolized him, presenting a false scene that suggests an attempted rape, a ruse designed to discredit him. The campers, no longer worshippers, drive him away. At the house, another ally manages to slip away—the one Sang-hyun only pretended to kill to protect her from Tae-ju’s reach.
Sang-hyun then drives toward a bleak, dawn-lit field, certain he must face the sun to end their shared existence. Tae-ju fights to hide, but Sang-hyun’s plan prevails: the dawn light is their final judge. They stand together on the car’s hood as the sun breaks, and both are consumed by flames, turning to ash as Mrs. Ra watches from the backseat, bearing witness to the end of a perilous, driven love that refused to fade.
