Episode 4 rounds everything out while simultaneously focusing on his career and the next steps. After a performance tribute to Jamal, Ed and Cherry get good news and reflect on a turbulent year.

In the last episode, despite disturbing revelations of wrongdoing at Three Mile Island before and after the accident, the utility fights to bring the plant back online. Its Unit 1 had its license temporarily suspended following the incident at Unit 2. Although the citizens of the three counties surrounding the site voted by an overwhelming margin to retire Unit 1 permanently in a non-binding resolution in 1982, it was permitted to resume operations in 1985 following a 4–1 vote by the Nuclear Regulatory Commission.
In 2017, it was announced that operations would cease by 2019 due to financial pressure from cheap natural gas, unless lawmakers stepped in to keep it open. Unit 1 shut down on September 20, 2019.
Billed as the worst nuclear incident in U.S. history, what’s particularly scary here is how close Three Mile Island incident came to becoming a national disaster. Without giving away the whole story, cost-cutting 'solutions' almost cause a catastrophic disaster.

From the frozen poles to the searing deserts, this episode shows how animals have come up with strategies to survive the uneven amounts of sunlight that fall on our planet over the course of a year. The exception is on the equator, where the duration of day and night remain the same throughout the year. Here, this guaranteed sunlight drives the great diversity of life in the tropical jungles.

As tides rise and fall twice a day, vast amounts of water swirl around the earth. This is a huge energy source that's currently largely untapped. An estimated 3000 gigawatts are available to be harvested globally, enough to power a third of the earth's homes. Yet compared to wind and solar, the technology needed to harness tidal power is still in its infancy. The power of the ocean’s tides is the last great untapped energy source on Earth. From sub-sea kites to floating platforms, teams of engineers are racing to perfect the technology to harness the vast flows of water.

Weather controls the distribution of freshwater on Earth. David Attenborough narrates how this uneven distribution has given rise to an incredible diversity of species and habits, from the driest desert to the lushest tropical rainforest. Featuring a colony of ants banding together into a raft every time its home in the Amazon floods, a rain frog that manages to eke out an existence in one of the world's driest habitats on Earth, and the last wild camels that survive the Gobi Desert's bitter winters by eating snow that blows in from Siberia.

Oceans are the largest ecosystem on earth, covering two thirds of our world’s surface and providing half the oxygen in our atmosphere. They are home to as much as 80 per cent of all life on earth, and nearly three billion people rely on them for their primary source of food.
But our planet’s oceans would be little more than stagnant wastelands, and life on planet earth would cease to exist, were it not for one simple factor: a global network of powerful ocean currents. Every drop of seawater on earth rides these currents, taking 1,000 years to complete a single circuit. Without the constant mixing of currents, tides and waves, our oceans would stop supporting life - and a healthy ocean is vital to a healthy planet.