Spoilt rich-kid Mia's world is turned upside-down when she is orphaned and whisked away to Mis Tor Manor on the edge of Dartmoor to live with her uncle and cousin Christopher. Mia is appalled to find herself in the remote countryside, in a freezing, crumbling manor. Grieving and missing her old life, she takes an instant dislike to Christopher, who never leaves his bedroom due to illness. Yet little by little, Mia starts to discover the beauty of this wintry world, and befriends local boy Daniel, who loves animals and teaches her how to ride a Dartmoor pony. One day she discovers a hidden door, covered in brambles and ivy, which leads to a walled garden. A special, secret place which needs someone's care to bring it to life once again so nature can flourish.