|Family||Sarah Teller - Wife (Deceased)|
Andrew Teller - Son (Deceased)
|First Appearance||"No Mercy"|
|Last Appearance||"The Black Rainbow" (Flashback Only)|
|Death||"Escape from Zona"|
|Cause of Death||Shot in the head out of mercy by Murphy|
|Series lifespan||"No Mercy" to "Escape from Zona"|
Before the outbreak started Harold was working with his wife Sarah Teller on studying mycology at Mercy Labs.
Dr. Harold Teller is held up at the compound of Mercy Labs together with a group of survivors. Harold ends up killing his wife, Sarah, out of mercy. He is later kidnapped by The Man for an unspecified reason.