Rosa has come from the city to live with Grandma Nan in the wilds of Big Sky Mountain. And what surprises are in store for her! Grandma Nan is not exactly an ordinary grandma, and Big Sky Mountain is like nowhere Rosa has dreamed about before. Grandma Nan lives in an old wooden cabin with Albert the moose and Little Pig the pygmy owl, and spends every day out on adventures. From canoeing down rapids to making friends with the local animals, life never stays still for long on Big Sky Mountain! Rosa has a lot to learn, and when unexpected visitors to the mountain cause a bit of a ruckus, can she rise to the challenge, and be the mountain girl Grandma Nan needs her to be?