Chris Packham reveals the underground world of badgers, water voles and rabbits. In specially created full-scale replica burrows it is spring, and baby burrowers must grow up fast, ready to take their first steps above ground. The programme reveals how baby rabbits learn to bond and looks at orphan badgers as they grow up. Will the water voles manage to produce their first litter? And how does a mole survive its solitary life almost entirely underground? In another first, the team excavate a massive abandoned rabbit warren in the wild by casting it in concrete.