Professor Peter Maxwell is in desperate straits. En route to an interplanetary research mission, he was snatched by a strange, shadowy race to a previously uncharted planet. Ancient beyond comprehension, this planet is a storehouse of information that would be invaluable to the people of Earth-even an Earth so far advanced that perfected time travel allows goblins, dinosaurs, ghosts, even Shakespeare to coexist. His attempts to interest the rulers of Earth are thwarted, however, by a startling discovery- Maxwell was ingeniously duplicated. The "other" him came back before he did, and soon after was "accidentally" killed. Now no one will believe the original Maxwell really exists...