Soon after her return from a business trip to Hong Kong, Beth Emhoff dies from a flu-like illness. Her young son dies later the same day. Her husband Mitch, however, seems immune. Thus begins the spread of a deadly infection. For doctors and administrators at the U.S. Centers 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 panic sets in.