Thomas is told to deliver a Christmas tree to the Mountain Village with Toby, but becomes cross when he has to use his old snowplough. A rock on the line smashes Thomas' snowplough into a water tower. Thomas is determined to go the rest of the way without a snowplough.

Henry has an unfortunate accident, leading to Diesel returning to the railway. Diesel is insistent on proving that he is the strongest engine in the world, much to the trucks' amusement. They edge him on to pulling twenty trucks at once. Diesel pulls them so hard that he breaks loose, falls off the quay and lands on a barge.