Thomas is asked to take the Fat Controller to switch on the Christmas tree lights at the Town Square after he's finished all his other jobs. On his way, he meets Percy who has been pushed by some troublesome trucks. Thomas tells Percy that he has a special job to do, which upsets Percy; he's finished his jobs, but he hasn't been given a special. Thomas doesn't want Percy to be sad, so he agrees to share his special with his best friend. Thomas tells Percy to wait in the siding until he's finished his jobs and Percy warns Thomas to take care; snow can be tricky. Thomas is sure he knows all about snow and ignores the warning. Thomas puffs to the docks where he's coupled to a flatbed of machinery destined for Maithwaite station. On his way to Maithwaite, Thomas speeds past Percy, inadvertently spraying his friend with snow. Percy calls to Thomas to slow down, but Thomas doesn't hear him.
After delivering his machinery to Maithwaite, Thomas heads to his next job at McColl Farm. Once there, he is coupled up to a flatbed of milk churns. On his way to the dairy, he passes Percy and snow sprays over him again. This time he is completely covered! At the dairy, Thomas is uncoupled and all of his jobs are now complete. Thomas races back to collect Percy, but he can't see him anywhere! Thomas soon becomes anxious as he still can't see Percy and is running late. Then Gordon thunders past, spraying snow over a small bush at the side of the line. This makes Thomas think that he can't see Percy as he must have sprayed him with snow, completely covering him like the bush. Thomas spots a big snowy shape next to him and decides it must be Percy. His decision proves to be correct, when a lump of snow falls revealing Percy's face. Percy is sad; his firebox has gone out, so he won't be able to come, and share Thomas' special. Thomas is sorry and confesses that his friend was right, snow is tricky and he knows nothing about it. Thomas has an idea and promises that Percy will share the special.
Thomas races to Knapford where the Fat Controller, dressed as Father Christmas, is waiting. Thomas tells the Fat Controller his plan to take the winter party to Percy. The Fat Controller thinks it's a grand idea and they set off to the Town Square. Once there, the Fat Controller turns on the Christmas lights and then invites the children to board Annie and Clarabel. Thomas soon arrives at the siding, where Percy is still feeling sad. But he soon cheers up when he sees the children. Thomas declares that Percy the snow engine is the children's special surprise. The children cheer and even the Fat Controller chuckles!