When a mutation of the virus is discovered in a local marketplace, China sends an emergency summons to Dr. Iris Varnack (Joely Richardson) of the Epidemic Intelligence Service. When she arrives, she discovers her efforts may be too late - an American businessman has become the first victim of a strain that is passed from human to human. As the flu begins its insidious spread, Secretary of Health and Human Services Collin Reed (Stacy Keach) races to combat the ensuing chaos. The victim's wife, Denise Connelly (Ann Cusack), does what she can to help other infected people. It wasn't supposed to happen this way - until it did.