It is 1979, and the Muslim world is on edge:Ayatollah Khomeini returns in triumph to Iran on February 1, and ten months later the Mahdi, the Muslim messiah, is presented to the pilgrims in Makka as the promised restorer of faith and justice. Which ancient prophecy of Muhammad is about to be fulfilled: "A person will be sent at the beginning of every century to revive Islam" or "A man [the Mahdi] from among my progeny will rise and fill the land with...