On the Jurassic Coast of Britain a remarkable 200 million year old fossil is discovered - the bones of an ichthyosaur - a giant sea dragon that ruled the oceans when the dinosaurs ruled the land. In this one-hour special for BBC One, Sir David Attenborough brings a passion project to the screen as he joins the hunt to bring this ancient creature's story to life. The bones were spotted by experienced fossil hunter, Chris Moore, but are trapped high within crumbling cliffs in Dorset. Chris and his team have to dig them out by hand before winter storms arrive. The bones are so well preserved that the team of scientists are able to use the latest techniques to analyse them - giving us new insights into the lives of these remarkable creatures. This could be a completely new species of ichthyosaur. The extraordinary fossil is covered in preserved skin which leads to new revelations about how these predators looked. As the story unfolds, David compares the sea dragon to animals alive today including dolphins, crocodiles and leatherback turtles. When Chris reveals more of the fossilised bones the investigation takes a surprising twist - as the team realise that they are dealing with a 200 million year old murder mystery story. Through painstaking forensic work they reveal that the sea dragon was most likely attacked by the most fearsome of all the ichthyosaurs of that time - the Temnodontosaurus. Using state of the art imaging technology and cutting edge CGI the team build the skeleton and create the most detailed animation of an ichthyosaur ever made - bringing it to life as well as reconstructing its fate.