In downtown Los Angeles, an earthquake strikes. Michael 'Mike' Roark, the head of the city's Office of Emergency Management or OEM, insists on coming to work to help out with the crisis, although he has been on vacation with his daughter Kelly. His associate, Emmit Reese, notes that the quake caused no major damage, but seven utility workers are later burned to death in a storm drain at MacArthur Park. One escapes and survives, but is severely burned on one side of his face. As a precaution, Roark tries to halt the Red Line (Los Angeles Metro) that run parallel to where the deaths took place, but Los Angeles MTA Chairman Stan Olber mulishly opposes, feeling that there is no threat to the trains. Against regulations, Roark and his coworker Gator Harris venture down the storm sewer in the park to investigate. They are nearly burned alive and barely escape when hot gases suddenly spew out of a crack in the concrete lining and flood the tunnel. Geologist Dr. Amy Barnes believes that a volcano may be forming beneath the city with magma flowing underground. Unfortunately, she has insufficient evidence to make Roark take action.