An earthquake reaching a 10.5 magnitude on the Richter scale, strikes the west coast of the U.S. and Canada. A large portion of land falls into the ocean, and the situation is worsened by aftershocks and tsunami.
The West coast of Northern America suffers an unprecedented series of major earthquakes in a matter of days, puzzling seismologists, including Dr. Jordan Fisher's team. His maverick assistant Samantha Hill comes up with a theory, which they confirm on site, that a deep tectonic rift links them and is likely to sink most of California into the Pacific. The only imaginable countermeasure are subterranean nuclear explosions. Three succeed, one rather causes a new problem. Meanwhile federal and other authorities as well as various people wrestle with side-effects like landslides and cope with a huge refugees exodus.
- Part 1 (aired 2/5/2004)
The beginning of the film shows a biker riding through the Seattle, Washington area when he realizes that a large earthquake is underway. Dr. Samantha Hill is awoken by the earthquake. At the Earthquake Center, the earthquake's magnitude is being recorded. The biker escapes collapsing buildings and stops under the Space Needle, a landmark whose legs succumb to elongating cracks. The biker speeds away to escape its collapse, but dust and shadow engulf the biker, his fate unknown. The magnitude is measured as 7.9 at the Earthquake Center. Dr. Hill goes to the Center after receiving a phone call, taking command and displacing the dismayed Dr. Jordan Fisher. Dr. Hill's Hidden Fault Theory is then explained.
In a basketball game between President Paul Hollister and Roy Nolan, President Hollister foreshadows that when Nolan is in a desperate position in the game he takes the long shot. The President's aide, Sean Morris, enters the gym and informs the President of the situation. At a local hospital Dr. Zach Nolan, Roy Nolan's son, and Dr. Owen Hunter are performing surgery. Nolan shortcuts his way through the surgery, risking the patient's life but saving him some scar tissue and a pint of blood. Hunter complains about Nolan's refusing help.
A magnitude 8.4 earthquake (considered an aftershock of the 7.9 Seattle earthquake) opens a crack which engulfs an entire train east of Redding, California. As a result, Governor Carla Williams, who had just seen her daughter and her ex-husband off on a camping trip, agrees to help the Governor of Washington.
Amanda Williams and her father Clark Williams arrive at a fictional town named Browning, where everything is covered in a thick red haze. Clark and Amanda, despite Amanda's asthma, emerge from the car and descend into the pit that used to be Browning, curious after they hear country music coming from it. Clark digs until he finds the source of the music: a car with a dead family in it. They drive back, trying to get home, but they get trapped in quicksand. Amanda and her father Clark narrowly escape.
Following yet more earthquakes and per the President's instructions, Roy Nolan constructs a task force of the best geologists and seismologists. The team includes Dr. Fisher and Dr. Hill. Dr. Hill mentions her Hidden Fault theory, which is received sceptically. When Nolan starts to realize that Hill might be right, she is given permission to prove her theory. She and Dr. Fisher visit a lake, where they see some dead animals with no visible cause of death until Dr. Hill realizes that they have died from carbon monoxide poisoning. The two sprint back to the car to get gas masks, but Dr. Fisher passes out. Hill frantically searches and eventually finds the masks, putting them on both herself and Fisher.
Back at the Task Force Center, Dr. Hill predicts that the next quake will be near San Francisco, California. When she brings the proof and prediction to Nolan, he deems it too risky to evacuate the entirety of San Francisco. Later, a 9.2 magnitude earthquake destroys San Francisco and the Golden Gate Bridge. This vindicates Dr. Hill, with Nolan remorsefully contacting the President, doubtful of his own ability to handle the job. Also in San Francisco were Governor Williams and her assistant Rachel.
Dr. Hill hypothesizes that they could "weld" the fault shut by letting it experience immense heat the only way she knows how is to do this is by way of nuclear bombs. This is the end of the first half of the series, in which we see what all the characters are doing.
Part 2 (aired 3/5/2004)
At the start of the second half, Nolan and others are preparing to install the first of six nuclear bombs at correct depths to "seal" the fault. The first five go smoothly, but during the installment of the sixth an earthquake occurs, and they lose a warhead. Nolan asks if he can set it manually and the answer is yes. Nolan goes down to do it, but is pinned by the warhead when an aftershock hits. He calls the President to say he failed, and the President urges him to "make the long shot". Nolan replies "Not this time, buddy, not this time". He then calls his son to say that he is sorry for being so distant and that he loves him. Zach Nolan, meanwhile, is at the refugee camp, "Tent City" in Barstow, California.
The Williams find a truck carrying survivors, and they are also transported to Tent City. In a wounded San Francisco, Carla Williams and Rachel are trapped under a wall. Rachel admits that she and her husband Jim had a horrible fight. She asks Carla to tell Jim that Rachel loves him and wants to have a family with him. The two women are found a few minutes later. Carla wakes up in a hospital in Carson City, Nevada and discovers that Rachel has died.
Deciding that nothing can be done about the lost sixth warhead, Dr. Hill decides to continue with the fault welding plan and detonate the first five nukes. At the last second, the sixth is activated by Nolan who manages to reach the control panel just in time. All six nukes were detonated and Nolan is incinerated.
It seems to work, until Dr. Hill, concerned about southern California, observes a river flowing backwards, draining into the open fault. The last nuke wasn't deep enough when it exploded leaving Southern California still in danger. Shortly after, a massive earthquake occurs. It climbs higher on the Richter scale, with Sean Morris narrating events to the President and the audience. Landslides destroy the Hollywood Sign. A massive crack appears at a beach near Venice, runs through Los Angeles and other cities, collapses the downtown skyline, and continues inland with the ocean pouring inside. Eventually the crack reaches Tent City and its peak of 10.5. Everyone runs from the crack and the rushing water. A tower falls on Dr. Fisher, injuring his leg. Owen Hunter joins his family and they escape. When Fisher collapses, the shaking stops. They stand up to see that the southwestern coast of California has been cut away and a new island was formed. The last scene focuses on what is left of the evacuation centers and zooms out to a view from space in which the California coast and the island are distinctly separated, with the President speaking about how this disaster was a wake-up call to the world that humans are not the masters of this planet.