You are david leatherhoof, you have been addicted to pills made from a unknown company, that make you see illusions, picking at your deepest and darkest fears. You go to the hospital to seek help. You meet monsters. the monsters are some kind of dark, demonic spirits from past patients, who were in disturbing, gruesome treatments that were in the hospital, that were released. the pills must have some kind of power to release the spirits only the consumation of the pills will release the demons... and when he turned off the lights... the demons were turned into the living dead, or possesed the patients there in that hospital.