A major catastrophic event happened while psychiatrist Judge Felter was doing genealogical research in the Granite Mountain Records Vault outside Salt Lake City. He and several survivors set off on foot for San Francisco in hopes of connecting with other survivors of the Big Melt. The story follows them as they adapt to the altered environment, which is now predicated on the sky's color, the wind's direction, and the search for food and water. It tracks their encounters with the Apostles, a demonic group that wanders the countryside, looking for loot and survivors.