In the second episode of the series, the Germanic tribes strike as Marcus Aurelius succumbs to disease, leaving a skeptical Emperor Commodus to prosecute a war that doesn't interest him.

This stylish mix of documentary and historical epic chronicles the reign of Commodus, the emperor whose rule marked the beginning of Rome's fall. In the first episode, the death of Marcus Aurelius brings a century of Roman triumphs and victories to an end, transferring power to his spoiled, unprepared son Commodus. When his father bequeaths him the world's mightiest empire, he is forced to spill the blood of both friends and enemies alike to keep his crown.

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.

This episode provides an overview of the nature of electromagnetism, as discovered through the work of Michael Faraday. Tyson explains how the idea of another force of nature, similar to gravitational forces, had been postulated by Isaac Newton before. Tyson continues on Faraday, coming from poor beginnings, would end up becoming interested in studying electricity after reading books and seeing lectures by Humphry Davy at the Royal Institution. Davy would hire Faraday after seeing extensive notes he had taken to act as his secretary and lab assistant. After Davy and chemist William Hyde Wollaston unsuccessfully tried to build on Hans Christian Ørsted's discovery of the electromagnetic phenomena to harness the ability to create motion from electricity, Faraday was able to create his own device to create the first electric motor by applying electricity aligned along a magnet. Davy, bitter over Faraday's breakthrough, put Faraday on the task of improving the quality of high-quality optical glass, preventing Faraday from continuing his research. Faraday, undeterred, continued to work in the Royal Institution, and created the Christmas Lectures designed to teach science to children. Following Davy's death, Faraday returned to full time efforts studying electromagnetism, creating the first electrical generator by inserting a magnet in a coil of wires. Tyson continues to note that despite losing some of his mental capacity, Faraday concluded that electricity and magnetism were connected by unseen fields, and postulated that light may also be tied to these forces. Using a sample of the optical glass that Davy had him make, Faraday discovered that an applied magnetic field could affect the polarization of light passing through the glass sample (a dielectric material), leading to what is called the Faraday effect and connecting these three forces. Faraday postulated that these fields existed across the planet, which would later by called Earth's magnetic field generated by the rotating molten iron inner core, as well as the phenomena that caused the planets to rotate around the sun. Faraday's work was initially rejected by the scientific community due to his lack of mathematical support, but James Clerk Maxwell would later come to rework Faraday's theories into the Maxwell's equations that validated Faraday's theories. Their combined efforts created the basis of science that drives the principles of modern communications today.

Technology is opening up new possibilities for physical, sexual and romantic relationships with astonishing speed. But is seeking human connection virtually a positive step forward or are we stunting our intimate lives? In the first episode of this series, meet a cyber BDSM couple who use tracking technology to fulfill their master slave relationship; an eligible bachelor in Japan who has fallen in love with a virtual girlfriend; and a revenge porn victim whose life was upended when her private naked photos were published online.

The Internet promises us escape from reality. We can go places we never thought possible and express ourselves as never before. But as we sit in our homes surrounded by screens, are we free... and safe? In this episode meet a woman pulled into an online cult from the safety of her bedroom; a former pilot who suffers from Electromagnetic Hypersensitivity and can only find relief in the absence of electricity and wifi; plus, a quadriplegic who uses cutting-edge adaptive robotics and virtual reality to transcend his body's limitations.