Dr. Niko "Nick" Tatopoulos, an NRC scientist, is in the Chernobyl exclusion zone in Ukraine researching the effects of radiation on wildlife, but he is interrupted by the arrival of an official from the U.S. State Department. He is sent to Panama and Jamaica, escorted by the military, to study a trail of wreckage across land leading to the recovered Japanese fishing ship with massive claw marks on it. Nick identifies skin samples he discovered in the shipwreck as belonging to an unknown species. He dismisses the military's theory that the creature is a living dinosaur, instead deducing it is a mutant created by nuclear testing. The 120m long creature travels to New York City during the rainy season, leaving a path of destruction in its wake.
