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."

Fearless Nepali high altitude climber Nimsdai Purja embarks on a seemingly impossible quest to summit all of the world's 14 highest peaks with an altitude greater than 8000m (called eight-thousanders) in seven months, breaking by far the previous 7 years record. He named his adventure 'Project Possible.'

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.

David Attenborough joins an archaeological dig uncovering Britain’s biggest mammoth discovery in almost 20 years. In 2017, in a gravel quarry near Swindon, two amateur fossil hunters found an extraordinary cache of Ice Age mammoth remains and a stone hand-axe made by a Neanderthal. Professor Ben Garrod joins the team at DigVentures during the excavation as they try to discover why the mammoths were here and how they died. Could the Neanderthals have killed these Ice Age giants?

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.

Scientists and engineers fight to save Notre Dame Cathedral after the 2019 fire. When the roof of Notre Dame Cathedral erupted in flames in April of 2019, firefighters battled for nine gruelling hours to save the historic landmark. Still, Paris came alarmingly close to losing more than 800 years of history. Now engineers are in a different race against time: to rebuild the roof and secure the medieval structure of Notre Dame. Underneath the charred scaffolding and vaulted ceilings of the cathedral, scientists study the components of Notre Dame’s iconic structure to puzzle out how best to repair it.