A big freeze has fallen over Pontypandy, and with the snow comes a lot of trouble! Sarah and James attempt to take the winning photograph for a competition, but they accidentally cause an avalanche and find themselves trapped in a cave. When Trevor is distracted, showing off to Dilys, he looses control of his bus full of passengers and they find themselves stranded on a frozen lake. Meanwhile Norman and Derek get up to their usual pranks and unknowingly create a giant snowball that starts to roll around Pontypandy. Thank goodness for Fireman Sam - join him and the rest of the rescue team as they save the day.