Beginning with the separation of the fuzzy thinking and pious fraud of astrology from the careful observations of astronomy, Sagan follows the development of astronomical observation. Beginning with constellations and ceremonial calendars (such as those of the Anasazi), the story moves to the debate between Earth and Sun-centered models: Ptolemy and the geocentric worldview, Copernicus' theory, the data-gathering of Tycho Brahe, and the achievements of Johannes Kepler (Kepler's laws of planetary motion and the first science-fiction novel).

In Egypt, Caesar rebukes the advisers of the boy king, Ptolemy XIII, for their presumption in eliminating Pompey and demands the man who killed him. Caesar decides to intervene in the dispute between Ptolemy and his sister-wife, Cleopatra, to ensure both Rome's grain supply and his own access to Egypt's treasure.
Antony, in an unusual show of prudence, advises against this with only half a legion in Alexandria and Cato and Scipio still at large in Africa. In Rome, Brutus gets a chilly reception from Servilia when he returns home from Greece.

Feast your eyes on a reconstruction of the mega-city and its amazing buildings. Alexandria, built in the middle of rancid marshland, had become in less than a century, the greatest city of the Mediterranean. An ideal position at the crossroads of east and west, and one that brought her great riches. Huge, modern, gleaming white and cosmopolitan, like no other in antiquity, it created its own identity.
While the beauty of its planning, its great arteries, its temples and its ports would be equalled only by its openness to the rest of the world. And the monumental achievements of its sovereigns, still shrouded in mystery, we'll never cease to fire our imagination for millennia to come.