National Park Service Rangers Kathy West and Nathan Toland are the only ones stationed at Fort Jefferson, a restored Civil War fort sixty miles off Key West, Florida. Two overnight campers go missing, but before the rangers can investigate, shady Homeland Security agent Glen Larsson arrives to close the park due to a purportedly imminent red tide. Things quickly escalate out of control when mercenaries arrive to back up Larsson and imprison the rangers...