Soon after her return from a business trip to Hong Kong, Beth Emhoff dies from what is a flu or some other type of infection. Her young son dies a few days later. Her husband Mitch however seems immune. Thus begins the spread of a deadly infection. For doctors and administrators at the U.S. Center for Disease Control, several days pass before anyone realizes the extent or gravity of this new infection. They must first identify the type of virus in question and then find a means of combating it, a process that will likely take several months. As the contagion spreads to millions of people worldwide, societal order begins to break down as people panic.