In the epic conclusion to the Ice Age story, we discover how the Great Thaw brought the end of the Ice Age and changed the world as we know it. Steve Backshall and Michaela Strachan go in search of a long-lost land that once connected the UK to mainland Europe before the Ice Age ended. Steve dives beneath the waves hunting for signs that the sea floor was once land and the thriving heart of Europe. Back on dry land, Michaela is on a hunt to find out more about this ancient land and wants to know how it flooded. She discovers that, less than 10,000 years ago, there was a natural disaster of epic proportions that helped form the North Sea and cut the UK off from Europe permanently. But this disaster may have been the catalyst for humans to develop further. Steve explores how early humans quickly adapted to their newly flooded world by developing watercraft unlike any we see on the rivers today. Meanwhile, deep in the Arctic, Michaela is working with the British Antarctic Survey as they drill for ice cores from a remote glacier. The ice they recover could reveal how the climate is changing around the globe. Bizarrely, Michaela discovers how a warming world may actually create the perfect conditions to trigger a new Ice Age. But if the world were plunged into the deep freeze again, how might we as a species cope? Steve goes in search of answers and meets a survival expert who understands the terrible dangers we may face. And Michaela visits a site in the Arctic where they're preparing for a means for humanity to survive after an apocalyptic event.