Christmas is approaching and Bel is staying with Gran in her new flat. The flat is part of a grand old Victorian house which stands in beautiful gardens, perfect for exploring, but Bel is lonely playing on her own.
One snowy morning, Bel spots a friendly white cat who leads her under the branches of a large fir tree. There she meets Charlotte, a girl from the past who tells her the cat belongs to her poorly sister Sara. Sara has asked Charlotte to take special care of Snow until she’s better.
But the Snow disappears and Sara is asking for him. Can Bel help Charlotte find him?