A hero is just someone who acts selflessly, out of concern for others, at personal risk and without the expectation of reward. In this episode, Michael Stevens asks employees to help him run a seemingly dangerous experiment, to see if they would blow the whistle to stop him.

The Hayabusa2 spacecraft has just completed one of the most intricate procedures in space exploration. The first mission to deliver rovers onto an asteroid has now descended to its surface for a sample, before returning back to Earth in 2020.

In the aftermath of Japan’s devastating attack on the US Pacific fleet at Pearl Harbor, the Japanese Imperial Navy moves in for a knockout blow. A surprise attack against the island of Midway is planned to draw the remaining American aircraft carriers out for a decisive battle. Admiral Yamamoto devises a meticulous plan. But the attack is in the hands of his by-the-book Admiral, Nogumo. When a genius American code-breaker unearths their plans – the Japanese attack is thrown into chaos.

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.

Garrett McNamara recovers from the injuries he sustained at Mavericks and begins training to return to Nazaré for another season. While surfing at Indonesia's G-Land site, Garrett suffers more injuries that threaten to take him off the waves permanently. Meanwhile, a friend of Garretts catches an 80-foot wave at Nazaré, taking the world record from McNamara. McNamara resolves to continue his hunt for a 100-foot wave.

It is a dark, mysterious, and secretive world. A world of clandestine projects, secret rocket launches, and futuristic tech. In December 2019, the United States Space Force became the newest branch of the military. It will defend the vast infrastructure of satellites, currently orbiting largely unprotected above Earth, and be ready to attack if they came under threat. This is also the story of the race to build the ultimate space weapon.