Its soldiers struggle to contain the disease before it overruns the United States, and search for a mysterious woman who may be vital to the solution.

Captain Bannerman Clark is in the Colorado Army National Guard and is the Rapid Assessment and Initial Detection Officer in Charge, making him the always ready first man on the scene of any major disaster, trained to get the best intelligence on the situation and report to others who will take over.

The warden of the prison had travelled to California and had succumbed to the biological agent there, biting and infecting a young woman.

Dick Walters is travelling in the rural areas of Colorado to check on an outbreak of an infectious agent in sheep.

She is picked up by two delinquents along the way and runs amok with them for a bit, seeing a disturbing scene in a small town where the village kills a zombie.

Clark is determined to find Nilla after seeing her disappear, but his superiors force him to go to Washington to meet with and work for a civilian.

Clark returns to Colorado to work on the cause of the disease and later transfers to Las Vegas for a short time as the West Coast is eventually overrun by zombies.

Nilla continues on, psychically drawn to a house where she is met by a handicapped man who tells her she is the only one who can stop the source.