Sang-hyun's infection begins a downward moral spiral. Reconnecting with his weak childhood acquaintance Kang-woo, Sang-hyun starts a passionate affair with Kang-woo's abused wife, Tae-ju. Tae-ju manipulates Sang-hyun into believing Kang-woo brutally beats her, convincing the priest to drown Kang-woo during a night fishing trip.
After the murder, the lovers are plagued by hallucinations of Kang-woo's bloated corpse. When Kang-woo's mother, Madame Ra, suffers a stroke from grief and becomes paralyzed, she uncovers their crime. Sang-hyun soon discovers Tae-ju fabricated her severe bruises to trick him into killing her husband. In a violent rage, he breaks her neck and drinks her blood. Overwhelmed by grief and regret, he bites his own tongue and feeds his own blood into her lifeless mouth, resurrecting her as a vampire.
Unlike Sang-hyun, Tae-ju embraces her new nature without moral hesitation, hunting and slaughtering innocent people across the city. To stop their spree and prevent innocent believers from venerating him as a holy idol, Sang-hyun intentionally stages a scandalous scene in a church tent to alienate his followers. He then tricks Tae-ju into driving out before dawn to an isolated, barren coastal plateau.
Taking Madame Ra in the backseat as a witness, Sang-hyun throws their car keys into the brush and tears down their sunshades. As the sun rises, Tae-ju frantically tries to hide in the shadows of the vehicle, but Sang-hyun restrains her. The two burn to ashes together in the direct morning sunlight while Madame Ra watches silently from the car.