Colossal explosions shake a remote corner of the Siberian tundra, leaving behind massive craters. In Alaska, a huge lake erupts with bubbles of inflammable gas. Scientists are discovering that these mystifying phenomena add up to a ticking time bomb, as long-frozen permafrost melts and releases vast amounts of methane, a potent greenhouse gas. What are the implications of these dramatic developments in the Arctic? Scientists and local communities alike are struggling to grasp the scale of the methane threat and what it means for our climate future.

Sir David Attenborough investigates a unique site in southern England where amateur fossil hunters uncovered giant mammoth bones and evidence of Neanderthals. A team of paleontologists and archaeologists soon discover that the site preserves rare evidence of the extinct beasts and early human inhabitants of Britain dating to over 200,000 years ago. What skills did the early humans have to help them survive during the Ice Age? How did they hunt and protect themselves against formidable creatures such as mammoths? With hands-on experiments with replicas of Neanderthal-era spears and stone tools, the world of prehistoric Britain comes to life.