Professor Brian Cox journeys across the vastness of time and space revealing epic moments of sheer drama that changed the universe forever.
The series begins this epic exploration of the cosmos with a hymn to the great luminous bodies that bring light and warmth to the universe: the stars. It is estimated that there are two hundred trillion stars in the universe, each playing their part in an epic story of creation- a great saga that stretches from the dawn of time, with the arrival of the first star, through diverse generations until the arrival of our own star, the sun, and a civilization that has grown up in its light.

Tyson describes the discovery of cosmic rays by Victor Hess through high-altitude balloon trips. Swiss Astronomer Fritz Zwicky, in studying supernovae, postulated that these cosmic rays originated from these events instead of electromagnetic radiation. Also tells how Vera Rubin observed that the rotation of stars at the edges of observable galaxies did not follow expected rotational behavior leading to consider the existence of dark matter. This further led to the discovery of dark energy to account for the increasing rate of expansion of the universe. Tyson then describes the interstellar travel of the two Voyager probes. Tyson tells the Carl Sagan's role in the Voyager program, including creating the Voyager Golden Record to encapsulate humanity and Earth's position in the universe. Tyson concludes the series by emphasizing Sagan's message on the human condition in the vastness of the cosmos, and to encourage viewers to continue to explore and discover what else the universe has to offer.