In 1971, five college buddies from the University of Texas embark on a final road trip odyssey across the Mexican border before facing up to uncertain futures, in Vietnam and otherwise.

When terrorist action releases a secret government virus in the Houston Federal building, the employees become aggressive and homicidal. Federal officials quarantine the building to wipe out the infected and control the story, but a small group of uninfected are fighting to get out.

In effort to create the perfect nutria for breeding by the fur industry, a scientist and his assistant inadvertently create a brutal mutation that escapes into the nearby swamps.