A rash of murders taking place on subways at exactly 6 P.M. strikes up fear in the population of Tokyo. The mark of a serial killer is left on these seemingly random murders and a professional, Dr. Setsuko Suma, is called in to solve the case. However, she is just as baffled about the crimes and seeks the help of her ex-lover, Rei Aku (a cult deprogrammer). Things begin to tense up as Suma feels she is becoming more and more like the serial killer and as Aku tortures her with mind games.