In Seoul, a peculiar virus spreads rapidly, transforming individuals into grotesque beings with infectious abilities. Yeon-U, a student on a school excursion, anticipates drawing nearer to his crush So-Yeon. However, the trip takes a dark turn as Yeon-U and his peers face a harrowing reality. To outlast this crisis, these high schoolers must navigate a city overrun by the mutant cells, striving to flee before succumbing to the epidemic's grasp.