Lee Na-yeon infects Gyeong-su in Episode 3 of All of Us Are Dead , and the group finds out later in that same episode when Nam-ra exposes what she did.

What happens

  • Na-yeon wipes zombie blood onto Gyeong-su’s hand after he’s already injured.
  • The others only realize it was intentional once the truth is revealed in the broadcast room scene.

Quick note

That’s the episode where the betrayal is confirmed on-screen, so if you were looking for the exact reveal point, it’s Episode 3.