The eponymous Jeremiah is a semi-loner who has spent the last 15 years travelling back and forth across the United States, seeking out a living and looking for a place called "Valhalla Sector" (the remains of Raven Rock), which his father—a viral researcher—had mentioned to Jeremiah as a possible refuge shortly before disappearing into the chaos of "the Big Death." A stop in the Colorado trading town of Clarefield results in Jeremiah teaming up with another lone traveller named Kurdy, before being imprisoned by the town's warlord in a cell with a man named Simon, who wants to recruit Jeremiah for a vague and mysterious organization. With Kurdy's help, Jeremiah and Simon escape, but Simon is fatally wounded in the process.