In this final-season story line, former Christian-leader vampire hater Sarah Newland (Anna Kamp) has gone underground, dyed her hair darker, and adopted a new religious belief system. But our heroes, undead and otherwise, believe she’s the key not only to the deadly (or undeadly?) vampire virus, but also to its antidote. And in tonight’s episode, they find her, and question her… and, for good measure, chain her.