In 1991, a group of Iraqi commandos penetrate a secret American government lab, releasing genetically modified
rattlesnakes. Over the following years, the snakes breed and multiply.
In the present day, an earthquake drives them from the underground to
the surface, and the snakes infect whoever they bite with a fatal virus.
A small-town doctor tries to correct the situation, but the government
wants to hide the traces of its wrongdoings. At the end of the movie,
the Snake's lair is located and destroyed by an explosion, killing
apparently all vipers. But the last scene shows a viper who survived.