It's early winter and Grace and Aaron are thrilled when an unusually heavy snowstorm means schools are shut. Instead, they spend all day helping at the stables. There's lots to do, from digging paths through the snow to feeding hungry ponies. As more snow falls and the people of Greenfort find themselves struggling to get to the shops, Aaron comes up with a brilliant idea to help other people: the Snow Pony Express!

Using a pony and sledge, he and Grace are soon very busy helping out. But while they are out delivering an urgent food parcel, a blizzard strikes, forcing them to take shelter in a disused barn. When the blizzard stops, they discover they are snowed in. Now it's a race against time to rescue themselves and their ponies before night draws in ...