Plot

With the discovery of an incoming asteroid, the government of America formulate a plan to destroy it. When the plan fails, all the world can do is wait. The main impact zone is revealed to be Dallas, Texas. Generally, the plot follows the lives and reactions of several characters: an astronomer, her father, her son, two firefighters from Kansas City, two young doctors in Dallas and the heads of the government agency in charge of the situation.—P. Wong <pwong@nt.net>

Late one night, near Billings, Montana, a gas tanker is driving by when a small meteor suddenly hits in front of the truck. The driver attempts to swerve out of the way, but loses control and overturns and the tanker explodes, causing a massive fire.

The next morning, the fire is burning out of control, and it is reported that the tanker was hit by a lightning bolt. With the area evacuated, FEMA (Federal Emergency Management Agency) Director Jack Wallach (Michael Biehn), and a colleague, Adam Marquez (Carlos Gomez) are flying via helicopter over the area, inspecting the fire (which had spread to the surrounding area), when they notice that two people are still in the area. It's a man on the roof of his house, trying to save it from the fire that is all around them, despite his wife's protests.

Jack and Adam land and take the woman aboard, despite her angry protest and concerns of her husband. Her husband starts to suffer from smoke inhalation when Jack manages to get him aboard the helicopter. Jack just barely manages to escape as a propane tank causes a massive explosion and destroys the home. They escape.

Later that evening, at the National Observatory in Boulder, CO, 29-year-old widow Dr. Lily McKee (Annabella Sciorra), the director of the National Observatory, is observing the Fletcher comet which is going to pass by Earth on the 4th of July. The comet arrives only once every 4000 years. Later on, when she goes home and looks at some photos, she sees what she believes are asteroids travelling under the gravitational influence of the Fletcher comet.

The next day, she informs Jack and Adam of the possibility of an impact (if the asteroids get caught in Earth's gravity) and calls them to her observatory. She tells them of two asteroids: Helios and Eros, whose orbits from the asteroid belt have been disrupted by the comet and may hit the Earth. Helios would hit with the force of 1,000 Hiroshima bombs and generate temperatures five times hotter than the sun in the area of impact. Everything within a 150-mile radius would be destroyed and the impact would also spray molten rock another 70 miles.

Eros is 4 miles across (10 times larger than Helios) and would cause a global ecological disaster if it did indeed hit. Lily adds that if they are lucky Helios and Eros would be made of gas and ice in which case they would evaporate in the Earth's atmosphere itself.

Then, Max Jenson (Brian Hill), one of Lily's assistants, informs Lily, Jack and Adam that Helios is getting closer to the Earth and that the observatory in Mauna Kea, Hawaii had picked up some smaller asteroids that the National Observatory cannot see, and they believe that a small one hit Montana. Jack and Adam realize that the fire was indeed caused by an asteroid impact.

Later on, Lily and Max check Helios' trajectory and realize that it will indeed hit the Earth. Their numbers show that Helios will hit in the Kansas City, Missouri area within about 48 hours. The impact radius is estimated to be around 4 miles and significant damage 50-100 miles out. If it hits land, no one in a 20-mile radius will survive. They tell the president about it, and he orders that the city be evacuated ASAP, which means moving out 2 million people out of the predicted impact area. Lily calls her father Dr Charles Napier (who works in Dallas) and asks him to take her son Elliot for a few days.

Jack and Adam work tirelessly to implement the evacuation of the city. Ultimately Helios does hit, but it breaks up in Earth's atmosphere and only a fragment hits that causes major flooding as it destroys a dam, but the loss of life is minimal. Jack drives into the city to rescue two stranded firefighters and a drunk driver who struck their vehicle, and they all get caught in the flood. He and the firefighters survive, but the drunk driver dies.

Jack is then informed by Lily that Eros is, in fact, going to impact Earth. The core of Eros is solid nickel and is travelling 60 miles per second towards the Earth. Unfortunately, the impact of Eros will be an extinction-level event. The impact of the asteroid will kick enough dust into the atmosphere to block out the sun for several years and cause the next ice age. The Earth has 23 hours to prepare.

The United States uses three jet fighters each armed with a laser weapon to try a coordinated air-to-space attack to destroy the asteroid with support from the entire world, but due to a storm, the attack is only partially successful and although it destroys the asteroid itself, it breaks it up into many pieces that rain down on Earth. The biggest fragment hit Dallas, Texas where Lilly's son Elliot (Zach Charles) and father are and destroys the city, killing thousands.

Lily's father ends up trapped in the ruins of the hospital where he worked, while her son wanders off looking for help. Lily's father Dr Charles Napier (Anthony Zerbe) has juniors working under him including Dr Matthew Rogers (Michael Weatherly) and Dr Valerie Brennan (Jensen Daggett).

Lily desperately searches the city for her father and son. Meanwhile, Adam is killed by a refugee while addressing an evacuation camp. After a search, Lilly locates her father and with the help of nearby firemen (Ben Dodd (Don Franklin)), rescues him, but goes on to try to rescue Elliot while the soldier who accompanied her goes back to base, although a fireman does accompany her.

The two search the ruined city and finally locate Elliot in the crater at Ground Zero of the Eros fragment impact. Jack shows up to help in a helicopter, having learned their location from Lilly's former escort. He rescues Elliot and the four return to base where they watch the comet pass by Earth and are relieved it won't return to cause trouble for another 4,000 years.