In 1978, Mary Mattock has her first period, and due to menstrual psychosis, murders her parents with a hatchet. Deemed mentally unfit, Mary is placed in Kings Park Psychiatric Center, where she is raped and impregnated by a guard in 1989. This incident is covered up, and after being told her child was a stillbirth, Mary goes on a rampage through the hospital. The police find Mary wandering the grounds, and open fire on her after she throws the severed head of her rapist at them, ending her killing spree. "Mary Hatchet" subsequently becomes a folklore figure, with local youngsters celebrating the Mischief Night-esque "Blood Night" in her name.