Al Lester was the director of a hospital in the Arklay Mountains. Long since it closed down, he became a serial killer known as "The Axe Man".
Al was the husband of Dorothy Lester. He loved her very much and was very much devoted to her. After she contracted terminal cancer, she was injected with a last-ditch mutagen based upon the t-Virus. While this successfully fended off the cancer, it caused her to develop the disease. Albert was left devastated and without answers as to what truly killed his wife.
Years later, he returned to the Abandoned hospital (which still held his wife's cadaver, still in her room) and saw as a decorative plant grew due to the viral infection. This plant consumed Dorothy's body, causing Albert to envision it as a form of life after death. After this, Albert took on the persona of the psychotic murderer known as the Axe Man, having noticed the plant grew even more when fed animals, and later even took his obsession to the point of willing to murder and feed some campers to the monstrous being. By then, his physiology had started to mutate too. He no longer felt pain or cold, even when shot point-blank by a shotgun.
During the Raccoon City Destruction Incident, Alyssa Ashcroft and the other survivors from Raccoon City were led by Al to the hospital, intending to kill them and offer them to "Dorothy". However, this proved to be a fatal mistake when Alyssa and the survivors were capable of driving him away with heavy fire power, eventually discovering the process necessary to vanquish the insane anomaly that had consumed Dorothy.
Upon weakening the plant sufficiently, it released Dorothy's remains, and took down the hospital with it, as its roots were the only thing truly keeping it stable. Albert was killed by falling debris when the hospital collapsed, crushing him and the corpse of his wife together.