The Spencer Mansion, a foreboding estate located in the forests northwest of Raccoon City, was believed by the public to have been left abandoned shortly after its construction. In truth, however, the mansion was merely a cover to hide the existence of an underground genetics laboratory controlled by the pharmaceutical giant, Umbrella Inc. In the laboratory, Umbrella had secretly been developing biological weapons and were experimenting with a man-made mutagenic pathogen known as the Tyrant virus (more commonly referred to as T-virus).