Spring, 1945. Gyeongseong, under the oppressive grip of the Japanese occupation, hides a monstrous secret within its walls. Jang Tae-sang, a powerful businessman with hidden depths, and Yoon Chae-ok, a tenacious tracker driven by a personal loss, find their paths colliding. Whispers of a terrifying creature emerging from the abandoned Onseong Hospital reach their ears, drawing them into a dangerous investigation.
Driven by their own motives – Tae-sang seeking to protect his secrets and Chae-ok searching for her missing mother – they reluctantly join forces. As they delve deeper into the hospital’s chilling halls, they uncover a horrific truth: a program of twisted biological experiments conducted by the Japanese forces, leaving behind an abomination born from human suffering.
Their pursuit of the truth forces them to confront not only the monstrous creature but also the darkness within their own society. Collaborators, resistance fighters, and innocent civilians all become entangled in the web of secrets and betrayals. As the line between humanity and monstrosity blurs, Tae-sang and Chae-ok must decide where their loyalties lie and how far they’re willing to go to survive the night and expose the truth to the world.