Wood travels through war-torn Afghanistan, crossing the Oxus River into Central Asia and the Silk Road city of Samarkand where, in a drunken brawl, Alexander killed the friend who had previously saved his life.

Beginning with the origins of the universe in the Big Bang, Sagan describes the formation of different types of galaxies and anomalies such as galactic collisions and quasars. The episodes moves further into ideas about the structure of the Universe, such as different dimensions (in the imaginary Flatland and four-dimensional hypercubes), an infinite vs. a finite universe, and the idea of an oscillating Universe (similar to that in Hindu cosmology). The search into other ideas such as dark matter and the multiverse is shown, using tools such as the Very Large Array in New Mexico. Cosmos Update shows new information about the odd, irregular surfaces of galaxies and the Milky Way perhaps being a barred spiral galaxy

Richard Dawkins explores what science can tell us about death. It's a journey that takes him from Hindu funeral pyres in India to genetics labs in New York.Dawkins brings together the latest neuroscience, evolutionary and genetic theory to examine why we crave life after death, why we evolved to age and how the human genome is something like real immortality - traits inherited from our distant ancestors that we pass on to future generations.