Bel is nervous about spending the lead-up to Christmas with her grandma at Lamont House, a sheltered housing complex converted from a grand Victorian home. The mansion is beautiful, but eerie, too with its moving shadows and odd noises. One night, Bel is sure she sees a cat wandering across the grounds, even though no pets are allowed. She follows its footprints through the snow and is transported into the past. There she discovers Charlotte, a Victorian girl her own age.