Dr. Josh Keyes (AARON ECKHART) is a university professor who's been asked by General Thomas Purcell (RICHARD JENKINS) to investigate the simultaneous deaths of 32 people in a ten-block radius. He and old friend Dr. Serge Leveque (TCHEKY KARYO) figure out is has something to do with the Earth's electromagnetic field having gone awry, a theory confirmed by egotistical scientist Dr. Conrad Zimsky (STANLEY TUCCI).
They're soon presenting a worst case scenario to the Pentagon where they outline global Armageddon due to the Earth's core - that creates its electromagnetic field - having suddenly and mysteriously stopped spinning. Keyes predicts they have three months before things get really bad and maybe a year before unshielded solar rays fry all life on Earth.
Due to the depth of the core, he sees no way of remedying the situation. Zimsky, however, has an idea and soon everyone travels to the salt flats of Utah where they meet the eccentric and reclusive Dr. Ed "Braz" Brazzleton (DELROY LINDO). He's devised a way to travel to the center of the Earth via a specialized ship that uses ultrasonic waves to cut through rock.
After several months of making the ship a reality, Keyes, Serge, Zimsky and Braz are joined by NASA shuttle astronauts Major Rebecca "Beck" Childs (HILARY SWANK) and Colonel Robert Iverson (BRUCE GREENWOOD) and enter the Earth.
Under the watchful eye of NASA Control Chief Talma "Stick" Stickley (ALFRE WOODARD) and guaranteed trip anonymity by computer hacker Taz "Rat" Finch (D.J. QUALLS), the crew sets on a journey into the unknown where they hope to reach the core and restart it with a series of nuclear explosions, all before time runs out for them and the world.