In 1889, seventeen men die under mysterious circumstances, and spooked by recent events, the miners who populate the town leave in droves until there's nothing left but a shell of a community.
Earl Bassett's celebrity after defeating the Graboid attack against the town of Perfection has proved short-lived, until he's recruited by a Mexican oil company whose workers have found more than they bargained for under the soil.
Val McKee and Earl Bassett are in a fight for their lives when they discover that their desolate town has been infested with gigantic, man-eating creatures that live below the ground.
In a battle of man versus machine, Martin, a top neurosurgeon who's studying brain malfunctions that cause mental illness, delves deep into his own mind to save himself from a megalomaniacal corporation.