Alison Crosby is a passenger on the number seven train on the elevated IRT subway line. As she stares vacantly out the window she spots a tall, muscular man holding a knife to a slim, dark-haired woman. The man lunges at the woman as the train goes into a bend. "Did you see that?" Alison asked the other passengers. But they deny seeing the man and the woman. Alison got off at the next stop and called the police. "I just saw someone get murdered "...