This tale narrates one town's attempt to isolate itself from the rapidly spreading influenza of 1918. Commonwealth is a fictional lumber mill town in western Washington state. The owner of the mill that is the economic center of this small village proposes, and sells to the residents, the plan for keeping the rest of the infected world from bringing disease into their midst. The single road into the relatively remote area is blocked and guarded by a rotating cadre of armed volunteers. The plan begins to fail as a stranger, a soldier claiming to be from a nearby military encampment, appears begging for food and shelter. He attempts to cross the barrier and is shot by one of the civilian guards.

The reader is introduced to the key players and the role of each in the town and in the evolving drama. The local medical practitioner struggles to advise the people, encouraging them to go along with the hardships created by not having access to supplies or the pleasures of visiting neighboring villages. Underlying the isolation is a history of political battles with the union and with competing timber companies, which bubbles to the surface as Commonwealth begins to lose its internal solidarity.