Dr. Albert Lester was the director of a hospital in the Arklay Mountains. Dr. Lester lost his wife, Dorothy, in an illegal human clinical trial conducted by himself on behalf of Umbrella, resulting in the hospital's closing. Obsessed with Dorothy, he began seeing a giant man-eating plant as her reincarnation in 1998 and started murdering people on its behalf.
Starting in 1993, Dr. Lester began accepting bribes from Dr. Greg Mueller to illegally trial T-JCCC203 on cancer patients. Lester, who's wife Dorothy was in a terminal state, was put in the trial in his desperation. The trial was botched, however, and although both patients were cured of their cancer, one died and Dorothy herself mutated into a Zombie. An investigative journalist writing an article on the rumoured trials was killed and eaten by Dorothy, who later died in the ICU. The police investigated the hospital and it was shut down, though Dr. Lester did not face prosecution due to Umbrella's influence over the Raccoon Police Department.
Over the years, Dr. Lester developed a habit of returning to the hospital, unable to move on with his life. In the hospital's intensive care unit he discovered a mutant plant growing on the wall. He became obsessed with the plant's care, thinking of it as Dorothy's reincarnation to the point of hearing her voice coming from it. Dr. Lester began killing birds and dogs around Raccoon Forest and feeding them to the plant for nourishment, causing it to grow into other floors. By March 1998, he expanded to killing trespassers or luring hikers and campers to the hospital, wearing a hood and armed with an ax. In his feeding of the plant, Lester became infected with T-JCCC203 and began to mutate. He realised his body was changing when a victim fired at him with a shotgun.
Lester's violent actions in the area reached press attention in early September, due to the witness reports of him walking around Raccoon Forest with an axe, along with other reports as to the number of bird and dog carcasses dumped into the river. His supply of victims was slowed down by this point, however, as the mountains were closed off. When the t-Virus spread into Raccoon City's water supply later that month, refugees began fleeing into the mountains, which gave him a new supply of victims. One of these refugees was Alyssa Ashcroft. He was unable to kill her, and the hospital began falling apart when the plant was killed. Lester returned to the ICU rather than flee, and found his wife's preserved body. He was then crushed to death by falling debris while he held the corpse in his arms.