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 1940, France has fallen and Hitler orders Operation Sealion, the invasion of Great Britain. But first the Luftwaffe must defeat the RAF for seaborne landings to succeed. In July 1940 an epic struggle in the skies above England begins. Only a brilliant defensive system and the bravery of young pilots stand in the Luftwaffe’s way. Wave after wave of German bombers are attacked by British planes. Featuring the last interview with the youngest Spitfire-pilot in the battle, Geoffrey Wellum.

When Japan’s military expansion in the Pacific reaches its fever pitch, Roosevelt is forced to act. By cutting off oil supplies, he hopes to force Japan to back down. But far from sedating their imperial expansions, he pushes them to take one of the greatest gambles in military history – taking their entire striking fleet 4000 miles across the Ocean to attack the American Pacific fleet in Pearl Harbor. It’s a huge gamble, and if it goes wrong, it will spell suicide for Japan.