In the third episode, Will Smith crosses the Serengeti to catch one of the greatest events of nature. "An image, one and a half million wildebeests on the plains of Africa in the most dramatic migration on Earth, has stayed with me since around thirty years ago I picked up a National Geographic Magazine and saw it. And finally, I'm here to see it."

On the trail of tiger sharks in the Pacific, Will Smith explores the power of smell. Sharks have a sense of smell that's hundreds of times more potent and accurate than that of humans. An enormous part of their brain is dedicated to smelling, to finding their way through the vast expanse of the ocean.

Will Smith discovers hidden worlds of fast and slow in the Earth's oldest desert. Worlds where things go so fast or so slow we don't even know they're happening. This hidden world of speed is everywhere, even 80 feet underwater. Hundreds of tiny anemones, anchored to the rocks, but film them patiently, then speed it up, and this miniature world comes to life. A lizard's tongue is one of the fastest movements in the entire animal kingdom. An orca creates a shock wave by slapping her tail and that pulse can travel through the water at more than a thousand miles an hour. to stuns the herrings she hunts.

Will Smith confronts his fear of nature on powerful white-water rapids in Iceland. "Over five expeditions, I've followed explorers into situations that were straight-up scary. It was worth it to discover the Earth's wonders. But your boy was tripping more than once. Because when I see wilderness, you know, nothing but nature, I get nervous because I don't understand it."

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.

By August 1949 the USSR became the world's second superpower, thanks to its spies who had stolen America's atomic secrets. But by March 1953, Stalin is dead and KGB chief, Beria, is executed later the same year. Nikita Kruschev tries to reduce the power of the security service, splitting it into several sections...but it doesn't last and, soon, the KGB is back.
In the USSR, countless KGB operatives spied on opponents of the regime at home, guarded the state and party leadership, and abroad tried to find out as much as possible about the intentions of the NATO countries and, if possible, to sabotage them.