Peter Thornton doesn't believe in God. Or rather, he doesn't believe in one God. "All paths are valid," he teaches his university students. One evening he ventures to the archaeology museum and touches an artifact recently discovered from ancient Babylon.   At the touch he is transported three thousand years back in time to Old Testament Babylon. Somehow he knows the language--and the people know him as Rim-Sin, sorcerer and high priest to the gods of Babylon. The moment he arrives he is accused of murder--a murder Rim-Sin committed--and he must run for his life.   Against the backdrop of Nebuchadnezzar's court at its zenith, he and rival sorcerers vie with Beltshazzar, the Jewish upstart, for the king's favor. As Peter scrambles to get back to the twenty-first century he encounters a lovely young woman who has some disturbingly powerful arguments about the God of the Bible.   Peter won't get home until he has fallen from his pride. Fallen from his polytheism. Fallen from Babel.