Ellie Harrison explores the plight of some of our most endangered animals. From water voles to wildcats, Ellie finds out what is being done to bring them back from the brink. She looks at plans to reintroduce big cats like the lynx, and finds out more about the beavers and wild boar already at large in the British countryside.Ellie spends the day at a wildlife sanctuary in Kent, where she helps get the water voles ready for their winter health check. She ventures into the lair of a wild wolf pack, and she gets up close to a wildcat kitten that has already had a fight for life.During her time at the sanctuary, Ellie looks back at some of the wildlife winners and losers that have featured on the programme in the past. These include Julia Bradbury's visit to the Yorkshire Dales to take perfect pictures of red squirrels in the snow, and Matt Baker's journey underground to see how old man-made caves are providing the perfect habitat for horseshoe bats.There is also another look at John Craven's visit to the Lakes to see for himself the final chapter in the 20-year reintroduction of red kites.