When spirited eight-year-old Heidi finds and rescues an injured lynx cub from a trap, she names him Pepper and secretly nurses him back to health. But as the cub's playful antics draw unwanted attention, Heidi learns of industrial plans that threaten not just the cub, but the entire Alpine ecosystem. With her loyal friend Peter and ever-faithful St Bernard, Joseph, Heidi embarks on a daring night-time journey to return Pepper to his family, a brave adventure through the Swiss Alp.