Fred Dinenage investigates the gruesome killings of 3 young children by the real Friday 13th killer, Monster of Worcester - David McGreavy. On Friday 13th April 1973 the bodies of three children were found impaled on garden railings. The murderer? The family's lodger David McGreavy. Fred Dinenage discovers the critical mistake that cost the children their lives and asks what caused the babysitter to embark on such a barbaric killing spree.