"Patient Zero" is a story-only episode, which introduces the final timeline of events.
Story
The scene starts off with a monarch butterfly flying to a black background as it then lands on the edge of a bench as the background fades into what seems like a train station. As people walk out the train, a woman struggles to keep her balance as she stumbled out, face bloodied as she collapses, a pool of blood spreading as a crowd of people look on. The scene slowly fades to grey as it then transitions to a landline phone with an incoming call.