Prelude to Foundation (Foundation, Bk. 6)

In a time before the Foundations, psychohistory's creator Hari Seldon is made to stand before the Emperor of the crumbling Galactic Empire to present how his scientific theory of predicting the future might be applied to the real world.

However, Hari refuses to deploy his theory for political gain, setting off instead with reporter Chetter Hummin in a quest of a place to safely apply this theory: Earth, the original home of humanity.

All records of Earth have been lost to time. Hari will therefore have to look back into the past, in order to seal the future of humanity forever.