Season 1
Episodes
1. Episode 1
Inside Lee Byeong-chan's science lab, a student incurs a seemingly harmless bite. Shortly after, a fast-spreading outbreak soaks the school in blood.
2. Episode 2
The infected multiply in droves. Scrambling for their lives, Nam On-jo and Lee Cheong-san find safety with others inside a classroom — but not for long.
3. Episode 3
When one of the group is scratched while fighting a zombie, Lee Na-yeon demands they kick him out. Outside, the virus swallows up the city.
4. Episode 4
In need of a cellphone, two students take a risky journey to the teachers' office. Byeong-chan passes on critical information to Detective Song Jae-ik.
5. Episode 5
Martial law is imposed on the city. When Cheong-san is separated from the rest of the group, On-jo leads a mission to use a drone to locate him.
6. Episode 6
The group clears a path to Cheong-san using sound to draw away zombies, but a new type of threat surfaces. Nam So-ju breaks out of the quarantine camp.
7. Episode 7
To make it out of the music room and onto the roof, the students put into action their most perilous plan yet. Elsewhere, Jae-ik comes across a setback.
8. Episode 8
Jae-ik and his crew run into a student from the school. Na-yeon works up the courage to face her peers. The group shares confessions around a fire.
9. Episode 9
A disturbance at the camp shifts the military's understanding of the virus. A thunderstorm provides cover as the group agrees to keep on moving.
10. Episode 10
The auditorium quickly becomes a trap for the two newly united teams of survivors. Byeong-chan's video logs reveal a drastic solution to the crisis.
11. Episode 11
Though a surprise protector provides the group safe passage to their next stop, Yoon Gwi-nam is not far behind. The military makes a grave decision.
12. Episode 12
The students make it to the quarantine camp, each of them weighed down by tragic loss. Months later, they hang on to hope for a survivor.