Lucy Cooke and Colin Stafford-Johnson continue their adventure around the UK's wilderness with a look at forests. Lucy investigates how the success of the pine marten in Scotland is also helping a recovery of the animals in Wales. Colin travels deep into one of Britain's wildest places, Keilder Forest, and we go behind the scenes with the Wild Alaska team tracking down grizzly bears. We also discover the surprising blue beetle living in the heart of Dartmoor's wooded valleys and learn how the wild boar has made a comeback.