When a series of strange tremors shake Los Angeles, a top seismologist, Kimberly Stevenson is sent to investigate the quakes' epicenter, a desolate wilderness area known as the Angeles National Forest. Two-hundred miles from civilization, Kimberly and her son Justin set up a research facility in an isolated mountain cabin. The project takes an unforeseen turn when the two discover a mysterious man, Michael Brandies. Michael claims he's an L.A. businessman who was forced to parachute from his plane when it ran into engine trouble, but there's something about Michael that makes Kimberly uneasy. When Justin turns up missing, Kimberly learns the truth. She's stumbled upon a test site for black market miniature nuclear weapons. And Michael's not a businessman, he's a mercenary, sent to stop tomorrow's final nuclear test, a test Kimberly knows could trigger the most powerful earthquake California has ever known.