We always knew they were coming back. Using recovered alien technology, the nations of Earth have collaborated on an immense defense program to protect the planet. But nothing can prepare us for the aliens’ advanced and unprecedented force. Only the ingenuity of a few brave men and women can bring our world back from the brink of extinction.

After years of increases in the greenhouse effect, havoc is wreaked globally in the form of catastrophic hurricanes, tornadoes, tidal waves, floods and the beginning of a new Ice Age. Paleoclimatologist Jack Hall tries to warn the world while also shepherding to safety his son, trapped in New York after the city is overwhelmed by the start of the new big freeze.

Dr. Adrian Helmsley, part of a worldwide geophysical team investigating the effect on the earth of radiation from unprecedented solar storms, learns that the earth's core is heating up. He warns U.S. President Thomas Wilson that the crust of the earth is becoming unstable and that without proper preparations for saving a fraction of the world's population, the entire race is doomed. Meanwhile, writer Jackson Curtis stumbles on the same information. While the world's leaders race to build "arks" to escape the impending cataclysm, Curtis struggles to find a way to save his family. Meanwhile, volcanic eruptions and earthquakes of unprecedented strength wreak havoc around the world.