Clint Ferguson, Chief Security Officer at the Centex Contagious Disease Center, returns from a short scuba diving vacation. As he drives toward the Center, he notices a huge cloud above it that appears to be spreading rapidly. He realizes there must have been a major accident at the Center and that an experimental deadly virus may have been released into the atmosphere. The virus has many of the symptoms of anthrax and is designed only to affect humans. The main characteristic of the virus is that it is harmless at elevations over 4,000 feet. Millions are about to die as this deadly virus spreads.