Following the harrowing events at Green Home, the survivors are forced to venture out into the open world, where the monsterization phenomenon has evolved into a global crisis. Cha Hyun-su, now a special infectee who has retained his humanity, finds himself captured by the military and subjected to experiments as they desperately search for a vaccine to end the apocalypse. As the survivors scatter across different locations, they must navigate a landscape filled with both terrifying new monsters and the even more dangerous remnants of human society. The season expands the scope of the series, introducing the Bamseom Emergency Management Bureau and exploring the complex moral dilemmas of survival, evolution, and what it truly means to be human in a world where the line between man and monster has blurred.