Do-ha concludes that the death at the villa was an accident, but Ho-gae continues his investigation. Do-ha uncovers the dark side of the neighbours.

When a murder occurs at Myeong-pil’s villa, Ho-gae leaves his post and joins the case. Kang Do-ha joins the National Forensic Service.

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.

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.

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.