An earthquake strikes the city of Los Angeles. Mike Roark (Tommy Lee Jones), head of the city's Office of Emergency Management, insists, passionately, on coming to work to help out with the crisis, even though he has taken a vacation with his daughter Kelly (Gaby Hoffmann). His associate Emmit Reese (Don Cheadle) notes the quake caused no major damage in the city, but seven utility workers are later burned to death in a storm drain at MacArthur Park. Despite the city's Department of Public Works insistence that the incident had nothing to do with the tremor and was just an accident, Roark tries to halt the subway lines which run parallel to where the mishap took place as a precaution. Metro Chairman Stan Olber (John Carroll Lynch) declines, feeling there is no threat to the trains. Against regulations, Roark and a colleague Gator Harris (Michael Rispoli) venture down the storm sewer in the park to investigate. They are nearly burned to death when hot gases suddenly spew out of a crack in the concrete lining and flood the tunnel. Geologist Dr. Amy Barnes (Anne Heche) believes a volcano may be rapidly forming beneath the city with magma flowing underground (similar to the formation of the Mexican volcano Parícutin which emerged & grew tremendously in just one week) but cannot come up with enough evidence for Roark to take action.