For nearly a century, humans forgot their glorious past and huddled in a state of ignorance and fear. Scientists have uncovered evidence fro m around the world that indicates that the early Dark Ages may have be en triggered by an actual event that occurred around 535 A.D. Science writer David Keys believes that the cause was a natural phenomenon of cataclysmic proportions. Determined to discover the exact nature of th is catastrophe, and to understand its political, economic and social r epercussions, he embarks on a scientific odyssey that ranges from Gree nland to the Antarctica; from the Americas to the Far East. At the cen ter of a stunningly-complex chain of events seems to be a loud bang (a ccording to Keys this was a volcanic explosion equal to two thousand m illion Hiroshima size bombs.) The subsequent environmental calamity, h e believes, affected human civilization from Mongolia to Constantinopl e, precipitating plague, famine, death, great migration, the fall of t he great Mexican city of Teotihuacan, the Anglo-Saxon victory over the Celts, and may even have played a role in the rise of Islam.