Twins Lucy and Samuel know exactly what they want for Christmas — a puppy of their own! Mum and Dad take them to Battersea Dogs Home a few days before Christmas. Lucy and Samuel fall in love with a St. Bernard puppy called Snowy — and he certainly lives up to his name. One day, when Lucy has a fight with Samuel and storms off for walk with Snowy, a blizzard sets in and she gets hopelessly lost. Can Snowy use his survival instincts to lead her back home?