The disappearance and fate of the tomb of Alexander the Great in Alexandria is among the most momentous and tantalising of all the mysteries we have inherited from the ancient world. Generations of scholars and historians have succumbed to the allure of the quest.
Now archaeologist Pepi Papakosta is on a mission to find Alexander the Great's lost tomb. Excavating in a public garden in the center of Alexandria, Egypt, the city he founded 2,300 years ago, she has discovered a rare marble statue of Alexander, Greek treasures and secret tunnels. But Pepi's biggest find is an extraordinary discovery even she was not expecting.

Sagan reflects on the future of humanity and the question of 'who speaks for Earth?' when meeting extraterrestrials. He discusses the very different meetings of the Tlingit people and explorer Jean-François de La Perouse with the destruction of the Aztecs by Spanish conquistadors, the looming threat of nuclear warfare, and the threats shown by destruction of the Library of Alexandria and the murder of Hypatia. The episode ends with an overview of the beginning of the universe, the evolution of life, and the accomplishments of humanity and makes a plea to mankind to cherish life and continue its journey in the cosmos. The Cosmos Update notes the preliminary reconnaissance of planets with spacecraft, the fall of the Berlin Wall and the end of apartheid in South Africa, and measures towards the reduction of nuclear weapons.