The executive Beth Emhoff returns from a business trip to Hong Kong with a stop over at the Chicago airport, where she has sex with her former lover. Beth feels ill but she believes that the problem is jet leg. She travels back home to Minneapolis and spreads the virus to her son Clark and her husband Mitch. When Beth and Clark die, Mitch goes in quarantine where the doctors realize that he is immune to the mysterious virus. Meanwhile in Hong Kong, London and in a small province, people have the same disease. The American CDC and the World Health Organization give their best effort researching the virus that is spreading in a geometric progression. The outbreak is threatening the worldwide population of annihilation, unless a vaccine is well-succeeded. The scientists begin a fight against time.