At a government laboratory in California, a weaponized version of influenza is accidentally released, immediately wiping out most of the population of the world. The remaining survivors now split into two groups, one led by a benevolent elder and the other by a maleficent being, to face each other in a final battle between good and evil.
To this day it's still a very compelling and engrossing look at humanity, the will to live, and the mysteries of why we're incapable of working together to make life easy on one another.