Explorer Steve Backshall and wildlife presenter Michaela Strachan take viewers on a gripping journey into the heart of the Ice Age using stunning location filming from around the world. In this episode it's the battle of the early humans as Steve and Michaela uncover the David-and-Goliath story of Neanderthals versus Homo Sapiens as both species compete for survival. As the Ice Age comes to an end, we discover how the Great Thaw changed the planet as we know it. Through virtual production we witness the flooding of the Ice Age world and the birth of the modern age. And deep within the Arctic Circle Michaela uncovers the ultimate irony that global warming and the collapse of the Gulf Stream could trigger the next Ice Age.