When the "Captain Trips" flu epidemic wipes out more than 99% of the population, the remaining few immune to the disease set out in search of other survivors, all the while, experiencing visions of the nurturing Mother Abagail and the menacing figure of The Dark Man.

The Boulder Free Zone Committee looks to solidify their leadership and bolster the community with a town hall meeting, but Flagg continues to make inroads as he plots to destroy the newly-forming society from within.

Nadine and Harold's dark intentions continue to take shape. Meanwhile, the Committee's spies entrench themselves in New Vegas, where Flagg is building his own society, where officially-sanctioned sin and debauchery disguises a ruthlessly-enforced order. Back in Boulder, Frannie hatches a plan to confirm her suspicions of Harold while Mother Abagail seeks divine council.

While all of Boulder fears for Mother Abagail's safety, Stu organizes search parties to ensure her return, presenting an opportunity for Harold and Nadine. In New Vegas, Flagg recruits a dangerous new follower.

After seeing both the light and the dark, Frannie makes her stand.