What on earth could have provoked a modern day St. Valentine's Day massacre? On Valentine's Day, four members of the Coverdale family--George, Jacqueline, Melinda and Giles--were murdered in the space of 15 minutes. Their housekeeper, Eunice Parchman, shot them, one by one, in the blue light of a televised performance of Don Giovanni . When Detective Chief Superintendent William Vetch arrests Miss Parchman two weeks later, he discovers a second tragedy:...