 The horror of the Black Death, the merciless killer of a third the world s population in the Middle Ages, still sends atavistic fear through us centuries after its first appearance in 1348. For a century, that fear has been eased by the knowledge that its apparent cause, the Bubonic Plague, is controllable. However, disturbing analysis throws new light on an old horror. Recent evidence suggests that the Black Death was NOT the Bubonic Plague, and that the true culprit may have an impact on our future as well as our past.