Neil Oliver, Chris Packham, Andy Torbet and Dr Shini Somara explore the secrets of Orkney.
Chris Packham uncovers the secrets revealed by the DNA of Orkney's unique vole.
Andy Torbet tries to cross the Pentland Firth as the ancient Orcadians would have done.
Andy Torbet dives below the waves in search of the inspiration for the first stone circle.
