In this episode Cathy and Jo travel east to Poland.  Join them along the way as they cross borders and head into the primaeval forests of Bialowieza and the vast marshlands of Biebrza - both complex ecosystems, alive with the sounds of mammals, birds and amphibians.  The variety and abundance of species they encounter are astounding but also give them pause to reflect on what Britain has lost and why. With thanks to Tomasz Jezierczuk of www.wildpoland.com