This David Cronenberg Canadian horror classic starts with the murder of a young girl by a scientist who lives in the same apartment building as her. His technique for disposing of her is to use acid to destroy her internal organs and then he commits suicide.
During the following murder investigation, a doctor realises wthat the scientist was in fact conducting experiments on the use of genetically engineered parasites in organ transplants.
The horror continues to unfold when other residents of the building begin to show signs of illness as the parasites spread and cause massive destruction throughout.