Lisa Trevor has been subjected to a variety of horrific experiments for over 20 years at the Arklay laboratory, which has taken its toll on both her mind and body and left her a disfigured shadow of her former self. She is the daughter of the mansion architect George Trevor.
Her body was immortal due to the repeated experiments, which led to the discovery of the G-Virus. After attacking a number of female researchers, however, it was decided that Lisa would be eliminated to avoid further incidents. Although she showed no actual signs of life for 3 days following her disposal, her incredible vitality kept her alive and she returned to stalk the area around the mansion as if nothing had changed. The disoriented members of S.T.A.R.S. would later encounter her in and around the mansion.