A mythological creature stalks the halls of a museum during a society fundraiser in this cheap sci-fi horror genre knock-off of Alien (1979). Penelope Ann Miller stars as Dr. Margo Green, an evolutionary biologist at Chicago's Field Museum of Natural History who receives a shipment of artifacts from a colleague performing fieldwork in Brazil.
Among the contents are leaves containing a rare fungus that, unbeknownst to Green or anyone else, attracts the palate of a rapidly mutating, lizard-like monster called Kothoga that has stowed away on a Brazilian freighter and has found a subterranean route into the museum from Lake Michigan.
Before long, several museum employees have become decapitated snack food for the beast, which prefers to dine on human hypothalamuses and pituitary glands.
Despite dire warnings from the museum staff, a gruff coroner (Audra Lindley) and the investigating detective, Lt. Vincent D'Agosta (Tom Sizemore), the Windy City's oblivious mayor orders a black-tie museum fundraiser to proceed.
During the event, the building's high-tech security system locks Green, D'Agosta, the mayor, and many chi-chi party guests in with the hungry animal, forcing everyone to attempt an escape through an underground waterway with which Kothoga is all too familiar.