When the 'Captain Trips' flu epidemic wipes out more than 99% of the population, the remaining few immune to the disease—including Stu Redman, Frannie Goldsmith and Harold Lauder—set out in search of other survivors. While doing so, they experience visions of the nurturing Mother Abagail and the menacing figure of The Dark Man.

Musician Larry Underwood is on the cusp of his big break when "Captain Trips" strikes New York. Alone and wandering an empty city, he meets an alluring new acquaintance also desperate to escape. Meanwhile, an incarcerated Lloyd Henreid comes face-to-face with Randall Flagg, The Dark Man himself, who makes him an enticing offer.

Mother Abagail selects a surprising voice to be her conduit to her chosen Committee in Boulder: the young deaf man Nick Andros. The arrival of a disturbing visitor to the Boulder Free Zone, shakes the Committee and Boulder residents to their core. Elsewhere in the Free Zone, Nadine Cross is haunted by a childhood memory.

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. 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. Frannie hatches a plan to confirm her suspicions of Harold. 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 tragedy strikes the Boulder Free Zone, Mother Abagail tasks members of her Committee with a dangerous mission. Meanwhile, Harold and Nadine begin their journey to New Vegas to unite with Flagg and claim their reward.

Risking everything, the Boulder travelers face off with Flagg's followers in New Vegas, among them a very different - and pregnant - Nadine.

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