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.

Moscow, 31 December 1991: the Red Flag of the Kremlin is pulled down and replaced by the three-coloured banner of Russia, marking the end of the Soviet Union and of its ideologies. Illustrated with testimonies of top protagonists and Mikhail Gorbachev himself, the documentary recounts, day by day, the critical last two years that led to the fall of the largest and one of the most totalitarian empires of the 20th century.