Chris and the team visit Merseyside. Industry, trade and goods have come and gone, and so have the wild things. Dr Trevor Dines dons his wetsuit to discover how an invasive pond plant, New Zealand pygmyweed, has found a way to grow in the dark. Chris uses a frying pan to test the sticking power of a tiny barnacle, and Sally hunts for the dead bodies of lichen in a Tudor manor house loft, to find out how our environment has changed over the past 500 years.