‘The Enemy Within’ begins with volcanic super-eruptions and their devastating consequences such as the 1815 eruption of volcano Tambora in Indonesia, and ancient eruptions in Yellowstone, USA, and Toba, northern Sumatra. Volcanic explositivity index, eruption magnitude, and eruption intensity are explained. Volcanic landslides in Hawaii and the Canary Islands will, in the future, result in giant tsunamis wreaking havoc around the Pacific and Atlantic Ocean rims. But when will they happen? Finally, the fate of industrial cities, such as Tokyo, located near active fault-lines and in earthquake zone, and the resultant effects on the world economy are considered.