This man is an undercover operative with London Underground. Over the past five years he has killed over 400 people on the tube. Many of the crimes have gone unreported because the victims are not yet aware that they are dead. His killing techniques are so subtle many of his victims may survive for many decades, living full and happy lives before they perish in their old age. No doubt two questions have entered your mind: 1) Why does he do it? 2) How has this murderous individual remained undetected for so long? Both are excellent questions.